Rail passengers were today warned to expect two years of disruption on one of London's busiest commuter routes.
A new timetable with fewer trains is being introduced on the Brighton line while Gatwick Airport gets a £150m facelift.
The project to build a new concourse will involve temporary platform closures and a 30mph speed limit.
From May 17th Gatwick Express will operate two trains an hour instead of four during much of the day.
No Southern trains will operate the full length of the line between London Victoria and Brighton but some Southern tickets will be valid on the more expensive Gatwick Express.
Southern and Gatwick Express parent company Govia Thameslink Railway promised longer trains to try to ease overcrowding.