Emergency drill at Lambeth North

Firefighters outside the closed station

Last year's exercise involved a collapsed escalator at Southgate station in north London.

Bakerloo line general manager Penny Hazell said: "With a real incident, there would be no advance warning. That is why details are not revealed, enabling LU and the emergency services to treat the exercise as if it were actually happening. By doing this we are able test our emergency plans and improve upon them where necessary.

Emergency vehicles in Baylis Road

"Great care is taken to make these exercises as realistic as possible", she added.