Govia Thameslink Railway (GTR) today advised passengers to plan ahead for the biggest timetable shake-up in UK rail history in a month's time.
As the UK's largest rail franchise, GTR has published the new details of train services that will affect almost a million rail journeys a day in the southern half of the UK.
GTR runs up to 3,200 trains a day - one every 27 seconds - and the times of all of these will change under the improved timetable.
The new schedule will operate from 02.00 on Sunday 20 May across the GTR network from as far afield as Cambridge and Peterborough to Brighton and Southampton.Space for 40,000 more passengers into London at peak times will be added next month, a weekly capacity boost equivalent to the population of Bristol.
Major upgrades have been introduced as the GTR network, comprising Thameslink, Great Northern, Southern and Gatwick Express is the UK's most congested railway with passenger numbers doubling in 12 years on some parts.
GTR passengers will benefit from more frequent services and, by next year, 80 more stations will have direct services to central London stations such as Farringdon, City Thameslink and Blackfriars.
Expansion of service is a major step forward in the Government-sponsored £7bn Thameslink Programme, the upgrade project which includes the recently-completed £1bn upgrade of London Bridge station by Network Rail.
Over more than a decade, platforms have been extended, stations rebuilt, and power supplies boosted for longer trains. Signalling has been upgraded and track reworked to improve reliability and allow trains to travel at high-frequency through central London in "self-drive" mode. GTR has also undertaken the UK's biggest driver recruitment and training campaign.
Charles Horton, GTR Chief Executive, said: "A huge number of passengers will notice the benefits in terms of new journeys, better intervals between trains, improved reliability, and more capacity across a wide region.
"We are redeploying trains and crew and there may be some disruption, so we ask passengers for their understanding during the transition period of several weeks during which time a very small number of trains will not run.
"Almost a quarter of all rail journeys are taken on the GTR network and because of the necessary scale of the change we strongly urge passengers to check ahead as to how their journeys will be affected.
"Introduction of the new timetables is a major milestone in the delivery of RailPlan 20/20, our programme to modernise rail services, taking advantage of the new infrastructure and trains provided by the Thameslink Programme.
"These changes followed the biggest and most effective consultation of its kind during which we made hundreds of amendments, some substantial, in response to 28,000 responses."