Following the success of the original scheme, plans were drawn up to upgrade the network to cope with the increasing passenger numbers that have led to severe peak-time overcrowding.
Network Rail obtained planning permission and legal powers in 2006, funding was secured in July 2007 and construction began in October 2007.
Plans included rebuilding the station buildings at Farringdon (in conjunction with the Crossrail project) and West Hampstead Thameslink, total rebuild of London Bridge and Blackfriars stations, two new underground platforms at St Pancras International, a new tunnel north of St Pancras International to the East Coast Main Line to allow through services to Peterborough and Cambridge in 2017, and platform lengthening, now being completed.
A new 8 and 12 carriage fleet of Class 700 trains began entering service in 2016.

The London and South East Route Utilisation Strategy published in July 2011 lays out a provisional 24tph timetable.
South of London it would provide four trains to Brighton (one semi-fast, one stopping) and two each to Three Bridges, Horsham, East Grinstead, Caterham, Tattenham Corner, Tunbridge Wells, Ashford International, Maidstone East, Sevenoaks and Bellingham.
North of London there would be eight semi-fast trains to Bedford, four stopping trains to St Albans, two stopping and two semi-fast trains to Luton, two semi-fast trains to Peterborough, two semi-fast trains to Cambridge and four stopping trains to Welwyn Garden City.

Below is a provisional timetable for Thameslink once the upgrade is complete.
Following the success of the original scheme, plans were drawn up to upgrade the network to cope with the increasing passenger numbers that have led to severe peak-time overcrowding. Network Rail obtained planning permission and legal powers in 2006, funding was secured in July 2007 and construction began in October 2007. Plans included rebuilding the station buildings at Farringdon (in conjunction with the Crossrail project) and West Hampstead Thameslink, total rebuild of London Bridge and Blackfriars stations, two new underground platforms at St Pancras International, a new tunnel north of St Pancras International to the East Coast Main Line to allow through services to Peterborough and Cambridge in 2017, and platform lengthening, now being completed. A new 8 and 12 carriage fleet of Class 700 trains began entering service in 2016.
The London and South East Route Utilisation Strategy published in July 2011 lays out a provisional 24tph timetable. South of London it would provide four trains to Brighton (one semi-fast, one stopping) and two each to Three Bridges, Horsham, East Grinstead, Caterham, Tattenham Corner, Tunbridge Wells, Ashford International, Maidstone East, Sevenoaks and Bellingham. North of London there would be eight semi-fast trains to Bedford, four stopping trains to St Albans, two stopping and two semi-fast trains to Luton, two semi-fast trains to Peterborough, two semi-fast trains to Cambridge and four stopping trains to Welwyn Garden City.
Below is a provisional timetable for Thameslink once the upgrade is complete.
Thameslink