The connection from Blackfriars to the Charing Cross - London Bridge line was single track, and the four-track section from Charing Cross to London Bridge reduced to two tracks where the two lines joined creating a major bottleneck. An additional double-track section has been completed west of London Bridge and the line to Blackfriars is now double track. London Bridge station is being rebuilt at a cost of £1bn with additional through platforms and fewer terminal tracks and the track southeast of London Bridge is being remodelled to eliminate conflicting train movements.

With the completion of this final section of track to the west of London Bridge, the tracks are now in their final position through the station, waiting commissioning of signalling during a 10-day period between December 23 and January 1. During this time major re-signalling will take place around London Bridge and the final section of the new concourse and final five new platforms will open.

Once drivers have been trained and familiarised with the new section of track and its signalling, Bedford - Brighton Thameslink services will be able to serve London Bridge for the first time since January 2015 allowing journey times to be cut and service frequency to be increased.