To maintain the secrecy of the site, even during a countdown to war, it was envisaged that 4,000 essential workers would assemble at an outlying destination known as Check Point. Warminster fulfilled this function, and from there a fleet of army lorries would have transported staff to the CGWHQ site. About 210 senior Whitehall officials and their staff, similarly unaware of their destination, were to assemble at Kensington (Olympia) station on the West London Line, before setting off by special train for Warminster, then a short trip by bus to Warminster Infantry Training Centre. There they would be broken into small groups to conclude their journey with a lorry trip to Corsham. The Prime Minister was to remain at Downing Street until the last moment, before being transported to Corsham by helicopter.