Govia Thameslink Railway (GTR) – which operates Southern, Gatwick Express, Thameslink and Great Northern – is warning customers that there will be no trains on the ‘vast majority’ of its network on Wednesday, owing to national industrial action by the ASLEF union. Trains also did not operate on Saturday after Friday saw an amended timetable, with fewer trains, due to an overtime ban by ASLEF. This amended timetable will also affect passengers today (Monday), Tuesday, Thursday and Friday. On Thursday, first services will start later than normal. On Wednesday, a limited shuttle service will run between London Victoria and Gatwick Airport. "These trains will be extremely busy and will not stop at any other stations,” a GTR spokesperson said. "Queueing systems will be in place and passengers may not be able to board their chosen service, especially in the late evenings. “Passengers are strongly urged not to travel to or from Gatwick by train if they have an alternative transport option, and to leave plenty of extra time for their journey if using a train is essential.” As there are no trains across most of the country on Wednesday, there will be limited onward travel options from London Victoria, so travellers are urged to plan their whole journey ahead of time. GTR said the reduced timetables have been designed to ‘help passengers plan for their day’ – providing ‘greater certainty of train times’ with ‘fewer short-notice alterations’. However, passengers ‘should expect’ busier trains, ‘especially in peak hours, and longer waiting times’, GTR said. The train operator has contacted schools to ‘ensure they are aware’ and can ‘help ensure nobody is caught out’. Jenny Saunders, GTR’s customer service director, said: “We know how difficult this ongoing national industrial action is for our customers and we're really sorry for the continued inconvenience it’s causing. "So that you can travel with confidence, we’ll be operating the most resilient timetables we can, but when trains are running, they’re likely to be busier than normal, especially in the peaks, and you might need to wait longer than usual. "Please plan all your journeys carefully in advance, allowing plenty of extra time, and check again before you set off.” London Gatwick Airport said its ‘very limited shuttle service’ will be in place between Gatwick Airport and London Victoria between 5.50am and 11pm. A spokesperson added: “Roads and our car parks may be busier than normal as a result of there being fewer trains. Please check before you travel.”