The John Collins Big Dipper was a wooden roller coaster that had been a fixture of the Battersea Park funfair since the Festival of Britain. On that Tuesday afternoon, a train being hoisted up to the start of the ride broke loose from its haulage rope. The emergency rollback brake -- designed for exactly this scenario -- failed. The carriages began rolling backward toward the station, gathering speed as the brakeman fought uselessly with the controls. The back carriage jumped the rails and crashed through a wooden barrier. The other two carriages piled on top of it. Five children were killed. Thirteen others were injured, including one child whose sister died in the wreck and who suffered life-changing injuries.

The investigation that followed revealed a catalogue of neglect. After a fire had damaged the ride in 1970, second-hand rolling stock more than fifty years old had been purchased to replace it. The dog brake that should have stopped the runaway train had not been functioning properly. The structure itself, including the pedestrian emergency walkway, was in a rotted and unsafe condition -- so deteriorated that one victim who survived the initial impact fell through a decayed handrail to her death. Inspectors found fifty-one separate faults on the ride. Testimony at the Old Bailey revealed the Big Dipper had experienced mechanical problems in the weeks before the disaster, including another incident in which a train rolled backward without being stopped by the brake. Witnesses described managers who were often drunk and teenage staff who used drugs. The brakeman on the fatal run had been told to leave the ride and was never questioned by police.

Three men were charged with manslaughter. A committal hearing at Wandsworth Magistrates' Court began on 26 February 1973. The ride manager and its inspecting engineer were committed for trial at the Old Bailey. Despite the overwhelming evidence of negligence -- the fifty-one faults, the prior incidents, the rotting structure, the impaired staff -- both men were acquitted. In 1975, crash victim Arun Thakur sued the owner's son in the High Court and was awarded just five thousand five hundred pounds in damages. The funfair was shut down. Battersea Park returned to being a public park, and the disaster faded from collective memory.

The Battersea Big Dipper crash resurfaced in public consciousness only in 2015, when an accident at Alton Towers seriously injured sixteen people. Journalists seeking historical context rediscovered the 1972 disaster and tracked down survivors like Carolyn Adamczyk, who had carried the memory for more than four decades. In 2022, on the fiftieth anniversary of the crash, the BBC reported on efforts by survivors to secure a permanent memorial in Battersea Park. 'People were groaning and hanging over the edge,' Adamczyk recalled of the immediate aftermath. 'It was awful.' Today, Battersea Park shows no trace of the funfair. The stretch of ground where the Big Dipper stood is green and quiet. Five children died there, and for half a century London barely remembered.