On 12 December 1988 the 07:18 from Basingstoke to London Waterloo, a crowded 12-car train made up of four-car 4VEP electric multiple units 3033, 3119 and 3005, was approaching Clapham Junction when the driver saw the signal ahead of him change from green ("proceed") to red ("danger").

A third train, carrying no passengers and comprising 4VEP units 3004 and 3425, was passing on the adjacent line in the other direction and collided with the wreckage immediately after the initial impact.

[5] Twenty-two of the people killed were from Dorset and the New Forest, including the train driver John Rolls, who was from Bournemouth.

[8] Pupils and teachers from the adjacent Emanuel School, who were first on the scene of the disaster,[9] were later commended for their service by Prime Minister Margaret Thatcher.

[10] Rescue was hampered because the railway was in a cutting, with a metal fence at the top and a wall at the bottom of a wooded slope.

His eventual report included 93 recommendations, for changes to the working practices of both British Rail and the emergency services.

[19] There had been inadequate training, assessment, supervision and testing and, with a lack of understanding of the risks of signalling failure, these were not monitored effectively.

[23] Cab radios, linking driver and signalman, were recommended,[24] as was the installation of address system on existing trains that were not expected to be withdrawn within five years.

[32] In 2017, a Rail Accident Investigation Branch report into a serious irregularity at Cardiff Central on 29 December 2016 revealed that some of the lessons from the Clapham Junction crash appeared to have been forgotten.

Excessive working hours, cancellation of route-proving trains and lack of detailed planning were identified as contributory factors to the incident.

[33] A year later, a report into a collision at London Waterloo highlighted similar circumstances, saying that "some of the lessons from the 1988 Clapham Junction accident are fading from the railway industry's collective memory".