Network Rail have released an interesting Time-lapse video showing the new eastern section of bridge at Blackfriars being slid into place.
The replaced bridge is at the north end of the station, immediately past the original end of the platforms, but would normally have been hidden behind the now demolished buildings on the corner of Queen Victoria St and Blackfriars bridge.
The slide was originally planned to take place toward the end of November, but was delayed until Christmas when it was finally completed successfully (apparently taking just over 100 hours to complete). Work can now properly begin on altering the track alignment at the station as part of the ongoing Thameslink project.
Thanks to daimler_fan for the spot and Anonymous for the location clarification.