On the evening of 4 December 1957, two trains crashed in dense fog on the South Eastern Main Line near Lewisham in south-east London, causing the deaths of 90 people and injuring 173.

The 5:18 pm Charing Cross-to-Hayes service, comprising electric multiple units totalling 10 carriages and carrying nearly 1,500 passengers, stopped at a danger signal at Parks Bridge Junction on the South Eastern Main Line, under a bridge carrying rail tracks over the line.

[2] At approximately 6:20 pm it was struck from behind by a train from Cannon Street to Ramsgate via Folkestone, consisting of Battle of Britain Class 4-6-2 no.

Help was accepted from The Salvation Army, the Women's Voluntary Service, St John Ambulance Brigade and local residents.

An emergency timetable began at 6:10 am the following day, with local trains travelling through Lewisham, avoiding the accident, and main line services diverted to Victoria, another London terminus.

[1] Henry Chadwick, a member of the public who assisted at the accident, successfully sued the British Railways Board for the "nervous shock" he experienced.

The case, Chadwick v British Railways Board, an important precedent for 30 years,[5] was partly overruled by White v Chief Constable of South Yorkshire, 1999 2 A.C.

Although installation had been agreed after the Harrow and Wealdstone rail crash in 1952, priority was being given to main-line routes controlled by semaphore signals.