For these reasons, it is necessary to close the London Underground each night. Last trains leave central London around midnight, with the last trains stabled in their depots by 1am.The first trains of the morning are staff trains, leaving depots around 4am. It is possible to plan for a 24 hour service in advance for special occasions.For example, in recent years, there has been an all-night service at New Year.ll railway networks need to have their tracks checked on a regular basis. (In the days of British Rail, every peice of rail was checked every third day.) For safety reasons, these checks cannot be done during periods of intense operation. Moreover, checks in tunnels demand greater safety requirements.