London's emergency services are being called into action for a training exercise on the underground.
The live emergency exercise will take place at Tower Hill Tube station on the District Line on Sunday.
The station is already closed due to major track replacement work between Whitechapel and Earl's Court.
Roland Murphy, from London Underground, said good safety procedures are in place "but we can always build and improve upon them."
He added: "All participants are unaware of the 'disaster' until the exercise starts, so they treat it as real as possible."
London Underground is legally required to hold an emergency exercise on the network every year.
A police cordon will be erected around the station and Trinity Square, Savage Gardens, Wakefield Gardens and Coopers Row will be closed for most of the day.