King of the Underworld: Building The Thames Tunnel


On the 2nd of March 1825 the Thames Tunnel Company began construction of what they hoped would be the first tunnel beneath the Thames. On the banks of the river at Rotherhithe, bricklayers and labourers began their work as the curious watched on. The project had been garnering a certain amount of attention ever since it had been granted royal Assent the year before, and its goal was an ambitious one – the construction of a tunnel beneath the river large enough for both people and horse-drawn traffic to use. It was a goal that many thought was impossible.

Over the next few months, London watched as the company’s workforce went about their business under the supervision of the energetic Frenchman who had been appointed to be the Company’s Chief Engineer.

He was, the papers said, an engineering genius. During the Napoleonic wars he had invented the first ever automated manufacturing process for making rigging blocks and thus the Navy, who got through a staggering 100,000 blocks a year, loved him (although apparently not enough to pay his invoices). He had also invented the first true production line process, which he put to use making cheap, quality, mass-produced boots for the army.

True, the Navy’s apparent inability to locate their chequebook and the fact that the sole had fallen out of the boot market after the war had seen him confined to debtors prison, but whilst there he had designed an impressive bridge for the Neva at St Petersburg on behalf of the Tsar, and the British Government had become so worried about the possibility that he might leave the country that they ultimately paid off all his debts from the national purse.

If anyone seemed likely to build the Tunnel, therefore, it was he. But as the weeks wore on and a fifty foot wide circular brick tower began to loom larger and larger on the Rotherhithe skyline, people began to wonder whether maybe someone should have a polite word with this celebrated figure because…


…Wasn’t he meant to be going down not up?

Contrary to perception, however, the chief engineer knew what he was doing. In order to dig, he knew, you needed a shaft. For a project like this it also needed to be a big one – a deep, wide shaft lined with solid walls to hold the earth back. The digging and shoring of this would have been a dangerous and expensive enough task in solid ground, let alone in the soft earth by the Thames.

But this engineer had an idea.

As the tower got taller it also got heavier and, inch by inch, with scientific inevitability, it began to sink into the soft riverside earth. In fact, by June 6th 1825 the 40ft tower had, with a little bit of help (and with men digging out the inside as it went), sunk completely into the ground.

Marc Brunel, Chief Engineer to the Thames Tunnel Company, had just invented the Caisson.

When most people hear the name “Brunel” today it is Isambard Kingdom who springs to their mind. Isambard’s legacy is huge, and he is rightly considered one of the Greatest Britons ever to have lived. Yet many do not realise that it is to his father, Marc that Londoners (and indeed the world) arguably owe the greater debt. Marc’s work on the Thames Tunnel – which, remarkably, is still in use today – would be the seed from which all London’s major subterranean railways would grow. Although it would ultimately take more than fifteen years to complete and extract a brutal cost in both money and men, the construction of the tunnel would see Brunel face, and largely conquer, all the problems that had until then prevented large-scale subterranean tunnelling.

Marc Brunel by James Northcote

That a tunnel was required at all was a consequence of the massive increase in traffic to London’s ports that had occurred at the beginning of the nineteenth century. By the end of the Napoleonic wars, London was the shipping capital of the world – the Thames packed with tall ships waiting to load and unload at all hours of the day. As London increased in size, and as more and more shipping unloaded on the south side of the river, the Capital’s existing river crossings to the heart of the City (London Bridge and Blackfriars) became increasingly overwhelmed.

By Brunel’s time the need for a way to reduce pressure on these bottlenecks was acute, but building a new bridge simply wasn’t an option. Ironically, the very vessels that made a new bridge necessary also meant it was impossible to build one. Any bridge would have to be large enough to allow tall ships to pass underneath – an engineering and financial nightmare. Other cities had addressed the problem by building bascule bridges that could be raised, but the size of the Thames meant that it would be some time before a bridge of this style would be technically possible in London (Tower Bridge, built almost 50 years after the Thames Tunnel was completed).

Given the above constraints, it is perhaps not surprising that Brunel was not the first to think of a crossing that ran below the river rather than above. In 1708 Ralf Dodd, who had been responsible for the Grand Surrey Canal, sank a test shaft at Rotherhithe but declared the geology unworkable. Then in 1805 the Thames Archway Company – the brainchild of Cornish Tin Mine engineer Robert Vazie – attempted to dig a 5ft high tunnel beneath the river.

In both cases, it was the ground that ultimately foiled the projects. The earth beneath the Thames was soft and thus prone to collapse. Worse, the presence of the river above meant that any large space excavated soon fell in and flooded under the pressure of the water above. This prevented the use of traditional mining techniques and the only man so far who had seemed to have a solution to this problem was Richard Trevithick, who had been brought in to try and finish Vazie’s tunnel after repeated collapses. Trevithick’s solution was an expensive one, however – to use a series of coffer dams to remove water from the immediate area and then drop in iron tunnel sections from above. This was too risky (and costly) for the Thames Archway Company’s directors and the tunnel was thus abandoned (although Trevithick’s idea was sound – it was later used in San Francisco with some success).

Brunel, however, thought he had a better solution. Tunnelling had been on Brunel’s mind for a while. He had originally considered a tunnel for his river Neva project, and had watched Trevithick’s efforts with interest. His nautical experience – both from his work with the British Navy and from his time as a young officer in the French Navy before the revolution – had also fixed in his mind an image from nature – the humble shipworm. He had observed that the shipworm dug into a ship’s timbers by using shell-like projections either side of its head to do the cutting, and then eating and excreting the pulped wood.

It was this approach that Brunel initially sought to emulate – he would design a device that would cut through the earth and funnel the detritus through itself. Its own weight and presence would thus provide the tunnel with support while bricklayers following behind built the tunnel lining. Sadly, however, Brunel soon discovered that this would prove impossible – neither manpower nor the steam engines then available proved sufficient to be able to power such a machine.

Undaunted, Brunel modified his plans. Instead of a machine, it was people that Brunel decided to place at the cutting face. He designed an iron and wooden frame which he called a “shield.” Assembled at the bottom of the Rotherhithe shaft in November 1825, this was a frame of thirty-six small chambers, each large enough to hold a single man. Each chamber was fronted by a number of six inch horizontal boards, which could be removed by the chamber’s occupant allowing the small section of earth behind them to be excavated. Once this was done, the board could be replaced and jacked forward, keeping the rest of the earth back.

Brunel’s Tunnelling Shield

When each of the thirty six miners had excavated all their boards, the whole apparatus could be jacked forward, with the frame itself supporting the weight of the roof and bricklayers following on behind to fill in a more permanent lining. This lining would be brick, at least 2ft 6in thick and held together with a new type of Roman cement that Brunel himself had helped create.

It was slow progress, but it worked. Marc Brunel had invented the Tunnelling Shield.

For two years, inch by inch, the tunnel crept forward. It was brutal work beset by constant difficulties. London Clay would become gravel with little warning, and even with the shield acting as a support, flooding was a constant worry. As it was, the tunnel leaked constantly and this was a major problem for the health of all involved. It is worth remembering that the Thames Tunnel pre-dates Bazalgette’s own engineering feats and thus Brunel’s Thames was not just a river. It was also an open sewer and repository for industrial waste.

The Tunnel under construction

As early as 1826, Marc Brunel had been forced to leave much of the day to day running in the hands of his senior engineers. Ill-health and stress also wrought havoc on their ranks, however, not to mention on the miners, labourers and bricklayers who worked for eight hour shifts amidst the seeping sewage and oppressive air.

Luckily for Brunel, engineering ran in the blood. As his own health faltered, he found that he could increasingly rely on his son to take up the daily management of the project – not yet twenty, Isambard Kingdom Brunel became his father’s presence on the front line of construction. It was on the Thames Tunnel that Isambard effectively learnt his craft, and here that he demonstrated his strength and talent for driving forward large projects.

Isambard Kingdom Brunel, pictured later in life

By February 1827, the Tunnel had been driven forward about 300ft. This was a major achievement given the conditions of earth, water and air, but it was far slower than Brunel or anyone else had forecast. The project was already now well over budget and behind schedule. In an effort to do something to quell rising costs, the company’s directors ordered the workers wages reduced. This did more harm than good, and though later resolved, resulted in a strike that brought all work to a halt for a time.

The directors also decided, against Brunel’s advice, to open the works to public viewing at the price of a shilling a time. Brunel’s major objection to this was one of safety – the risk of flooding was still there, he insisted, and would only grow as the tunnel’s length increased. Brunel knew that the tunnel would soon be perilously close to the riverbed’s lowest point and by May workers were beginning to find debris such as coal and china in the leaks – suggesting that the tunnel was possibly even closer to the riverbed than they had planned. On the 18th May Marc was leading Lady Raffles and her party on one of the directors’ paid tours when he felt a feeling of real foreboding.

“[I was] most uneasy all the while,” he would later say, “as if I had a presentiment.”

That evening, as the tide in the Thames rose, the tunnel roof above the tunnelling shield broke. Water poured in, and the workers (and Isambard who was supervising them at the time) were forced to beat a hasty retreat to the Rotherhithe shaft.

With work now halted, Isambard went down in a borrowed diving bell to survey the damage. It soon became clear what had happened – gravel dredgers operating in the Thames had, contrary to the law, been dredging too deep. The tunnel had indeed ended up closer to the riverbed than expected, and this had led to the roof’s collapse.

Worse soon came for Marc. The damage was repairable and, under Isambard’s careful supervision, Marc had men lay iron roads across the breach and bags of clay dumped on top. When this had been completed, the tunnel was pumped dry and work began again (although the flood water left the air in the incomplete tunnel section even worse than before). All this put even more pressure on Marc’s health, however, and in August 1827 he suffered a paralytic stroke.

As he slowly recovered, with Isambard continuing to supervise the work, it soon became clear that the flooding had caused public confidence in the project to waver – potentially disastrous given the perilous state of the company’s finances. In an effort to restore faith, therefore, a rather effective public relations stunt was staged – in November 1827 a sumptuous banquet was held in the tunnel for the project’s backers.

George Jones’ famous painting of the banquet is the only picture featuring both Marc and Isambard together. Doubly impressive given that Marc didn’t actually attend.

The stunt worked. With the Coldstream Guards playing heartily in the background, and many notable guests in place (including the Duke of Wellington – who was a lifelong supporter of Brunel thanks to the Frenchman’s boot-making efforts) confidence was restored and work continued.

That confidence would not last long. On the 12th January 1828, as Isambard was supervising work in the tunnel, he noticed that two miners – Collins and Ball – were struggling with some shoring on the Tunnelling Shield. A hands on manager throughout his life, Isambard headed forward to help them out. Suddenly, as they worked, the three men were engulfed in a torrent of water.

The pressure threw the men back off the frame and shattered the wooden scaffolding behind on which the bricklayers worked. As water poured through the now-broken tunnel ceiling, men and material were thrown about like ragdolls. As the water sheeted down, Isambard found himself pinned beneath the remains of the broken scaffolding. Somehow, with the water-level in the tunnel rising quickly, he managed to free himself and crawled into one of the brick arches that ran down the centre of the tunnel bore. Sheltered briefly from the full force of the water, Isambard was able to pull himself up and survey for the first time the damage – he quickly realised that a major breach had happened. The tunnel was flooding – and fast.

Isambard ran.

As Isambard and the rest of the tunnel’s workforce raced towards the safety of the Rotherhithe shaft, the breach worsened. As the young engineer reached the shaft he realised the worker’s steps were crammed with those trying to escape. He turned and sprinted for the visitors’ stairs, but was suddenly swept off his feet by a vast wave of water that surged down the tunnel with such force that it pushed Isambard and several others who had not yet have reached the surface right up the shaft itself. Some – including a battered and broken Isambard – were lucky enough to be swept over the lip to safety. The unlucky ones were sucked back down to their deaths as the wave lost its force.

Six men died, including Collins and Ball. Unlike Isambard, they had been unable to free themselves from the wreckage of the scaffolding.

The flood had disastrous consequences for the tunnel. Not only was the damage greater than before, but it also robbed Marc of one of his most valuable resources – Isambard. His knee torn, his body bruised and (although he didn’t know it at the time) bleeding internally, Isambard had insisted on staying on site in the immediate aftermath and supervising the assessment of the damage by diving bell. Even Isambard’s capacity for feats of endurance had limits though, and he was soon forcefully packed off to Brighton and then Bristol to recover (he’d pass his time designing a bridge or two).

Deprived of his right hand, Marc went into overdrive. His days were spent supervising the repair efforts and speaking publicly in support of the project’s continuation. His nights were spent poring over the days’ work results and writing reports to the now-frantic company directors detailing the state of play.

Eventually the breaches were sealed, but just as work was about to begin on restoring the badly damaged tunnelling frames, the project’s finances finally reached critical point. The company needed an investment of funds to survive but despite the efforts of Marc and his ever-present supporter, the Duke of Wellington, who once again put his public reputation on the line and vocally supported Brunel, a subscription drive failed.

On August 9th 1828, the tunnel face, with the remains of the frames still in place, was bricked up. The Tunnel seemed finished.

Marc Brunel, however, wasn’t.

As soon as tunnelling ceased, Brunel began a relentless offensive aimed at securing the funds necessary to complete it – £250,000 all told. He lobbied financiers and businessmen, but soon realised that the only source of likely funding was the Government itself. Shockingly, in 1830 Brunel discovered that the Government itself had actually reached this same conclusion some time before, and had offered a loan to the company only to see it rejected out of hand by the Company’s then Chairman – a man who it now seemed had been almost willing the company to fail by the end.

By 1831 Brunel had, despite suffering a heart attack, managed to undo this damage and the Government now agreed that Brunel could seek to draw on the Treasury’s Loan scheme. At the Company’s AGM, Brunel had also seen the Chairman deposed.

Getting the Treasury to actually agree to a loan, however, proved incredibly difficult. The first proposal was rejected but Brunel continued to campaign, even lobbying the King himself. The second was approved only, heartbreakingly, for Brunel to see the Treasury Loan Scheme’s funding cut rendering the approval useless.

In 1834, after a third application had been rejected, a number of Fellows from the Royal Society decided to throw a dinner in Brunel’s honour. At the Spreadeagle & Crown Pub at Rotherhithe (now the Mayflower), they toasted the Engineer’s health and formed the “Tunnel Club” – a lobbying group determined to help Brunel bring his funding plans to fruition.

Finally, in June of that year, Parliament signed off on a £270,000 loan.

Work on the tunnel began again in 1835. The old, now rusted, shield was removed and a new one, its design improved by Brunel, installed in its place. The work of digging the tunnel proved to be even more brutal than before. Brunel had planned to transfer a significant amount of the effort to the Wapping side of the river, not least to allow ventilation to be taken over from there. The Treasury, however, refused to sign off the expense. The wording on the loan was very specific, they insisted – it was to complete construction that was already started and they would consider this as new work.

As a result, conditions below ground became positively horrific. The air was putrid, not helped by the fact that over 100 gallons of Thames filth was now seeping through the tunnel head every day, and gas was increasingly building up in the tunnel as well. This would lead to the occasional outbreak of explosions and small fires which would burn for days, rendering the tunnel even hotter to work in and leaving the iron-framed tunnelling shield sometimes scalding to the touch.

The government also rejected a plan by Brunel to buy his own diving bell. This, he’d determined, would have been the solution to the flooding problem – by having a diving bell above the tunnel head at all times Brunel hoped to be able to catch likely flood points in advance and reinforce them with clay bags before they broke. Brunel got his ship from which to distribute the clay, but not the diving bell and thus was largely reduced to throwing clay overboard blind in the hope that it would help.

Despite all this, the tunnel slowly progressed. Burned by flame, sickened by the water, vomiting and blinded by the gas, the cost to the workers was horrific. Lessons would be learnt for the future from the pains suffered by Brunel’s workers but that was little help to them now. Brunel repeatedly petitioned to be allowed his Wapping ventilation shaft, but was repeatedly turned down. Inch by inch, the tunnel crept forward and more and more the miners found themselves digging through mud rather than earth.

Then, on the morning of the 23rd August, the seemingly inevitable happened once again.

There had been some concern about the water levels in the tunnel since the night before, although nothing had come of it. Brunel himself had been at the site since 4am but left in the middle morning when nothing had developed. At lunchtime Thomas Page, Marc’s primary engineer now that Isambard had major projects of his own, was about to depart for a meeting with the company directors, but when he heard that the flow of water had increased slightly above one of the cutting frames something at the back of his mind told him not to go.

Instead Page headed down to the shield. All appeared under control but, still wary, Page ordered that a raft, clay and other breach-blocking supplies be readied. He also ordered the tunnel cleared of visitors and unnecessary personnel and that a note be dispatched to Brunel warning him that a breach may come at high-tide.

Page was correct – but it didn’t take until high-tide. By the afternoon water was rushing in and the workers, under the calm and controlled oversight of Page, were pumping out water and strengthening the tunnel to try and stem the flow. Ultimately it proved unsuccessful and Page was forced to order the evacuation, but his management of the situation meant that the breach was far less serious than it could have been. After the normal process of diving bell and clay bagging, work resumed on the 11th of September.

The Tunnel would flood three more times, the first of which happened whilst both Brunel and Page were ill and sadly cost a life. By now, however, the process of sealing breaches and cleaning the tunnel had become almost routine. Even during the third, when the water managed to take out all the lighting in the tunnel, the workforce remained composed and were able to minimise the damage. In all cases, work resumed with little delay.

Progress, however, was still painfully slow – just nine-tenths of an inch a day in some months – because the conditions below ground continued to worsen. Brunel, who turned 70 in 1839, was repeatedly bedridden. His condition was not helped by the fact that he would visit the site every two hours at all times of the day to check for potential breaches. Page too suffered.

Ultimately, however, it was the workforce who continued to suffer worst. Again and again Brunel lobbied the Treasury to allow him to build his Wapping ventilation shaft, but he was continually refused. As one newspaper at the time noted with morbid humour, the Government’s policy seemed rather “one-sided.”

On the 22nd August 1839 the tunnel reached the low-water mark on the Wapping bank. Work continued and on the 11th June 1840, work began on the main shaft at Wapping, to be constructed in the same way as the first at Rotherhithe. In May, as the Wapping shaft slowly sank and the main tunnel neared its final destination, a small drainage shaft was dug between the two. That June, Marc Brunel’s 3 year old grandson became the first person ever to fully pass under the river from shore to shore.

Finally, on November 16th 1841, Thomas Page climbed out of the Rotherhithe shaft and knocked on the door of Brunel’s house just a few metres down the road. On being ushered in, he presented the 72 year old engineer with a clod of earth. Brunel looked at it and smiled at Page, who smiled right back.

The clod was covered in red brick dust. The tunnel had finally reached the shaft. Brunel had successfully built a tunnel beneath the Thames.

The work did not finish there, of course, and it would not be until March 1843 that the Tunnel admitted its first paying customer. Even then, it was ultimately a financial failure. The money the Government had loaned the company proved enough to complete the tunnel, but not enough to build the huge descent ramps necessary for horse-drawn traffic to access the tunnel.

As a result, it could take foot traffic only. The tunnel was rightly recognised as an engineering marvel and became one of London’s biggest tourist attractions – 2 million people used it in that first year alone, but it had ultimately cost almost £500,000 to build. Without road traffic it could never repay that, and despite the company’s efforts to turn it into a bustling subterranean market and Christmas fair, it ultimately ended up as a refuge for the seedier side of London life.

The Tunnel shortly after its completion

In 1865, however, the tunnel finally found its use – it was purchased by the East London Railway and became a railway tunnel beneath the Thames. Since then the Tunnel has seen passengers, goods, armaments and even runaway sheep travel through its confines.

Indeed it is still at the heart of London’s railway network today – if you find yourself on the East London Line then look carefully as you pass through Wapping or Rotherhithe and you’ll see it.

The Tunnel in 1996 – before the massive renovation efforts that took place during the ELL rebuild. Courtesy English Heritage.

The Tunnel shortly before the revamped East London Line opened. Courtesy Caroline’s Miscellany

Almost two hundred years ago, Marc Brunel set out to do the impossible. At great cost in money, time and men he managed to accomplish something that no-one had ever done before, creating a tunnel that many then genuinely regarded as the eighth wonder of the world. In doing so he laid down the foundations for every major subterranean railway that would follow. Others would take the inventions he had created and the lessons he had learnt and improve on them, but to Marc Brunel goes the honour of proving that it could be done at all.

The Historian Peter Ackroyd once described Marc Brunel as “a lord of the underworld.” It is probably fair to say, however, that he is incorrect.

For both the engineering legacy he left behind, and the cost to both himself and others that it required, Marc Brunel wasn’t a lord of the Underworld.

He was its King.

This article first ran on London Reconnections in February 2011. We run it again here to mark the brief opening of the Thames Tunnel to walkthrough tours this weekend. Although tickets are (unsurprisingly) sold out, we thus hope to have photos of the current state of the tunnel next week.

Written by John Bull
John Bull is the Editor of London Reconnections. A transport journalist and historian, his writing often focuses on the political or strategic challenges facing London's transport network and beyond.