The first calls to emergency services came from members of the public, scrambling along the embankment in shock. The driver of a light engine on the adjacent track had seen the collision and managed to contact the signal box. Inside the box, alarms were already sounding - the impact had wrecked the signalling equipment - and the signalmen, trying to reach railway control at Waterloo, ran into confusion about exactly where the trains had collided. Police in East Sussex were initially called, fifty miles from the actual scene. The traction current's circuit breakers had tripped, but the supervisory circuits were damaged too, so nobody could confirm whether the live rail was truly dead. British Transport Police, the fire brigade, and ambulances converged on the cutting. A police helicopter ferried doctors in. By 3:15 the last casualty was on the way to hospital. The search of the wreckage continued until 5 p.m.

The Department of Transport report, published later in 1989, found no fault with the train or with the signalling equipment itself. Robert Morgan, the driver of the Littlehampton train, had missed the preceding caution signal and passed the danger signal that was protecting the Horsham train ahead. He pleaded guilty to manslaughter before the report was even published, and was sentenced to twelve months in prison plus six months suspended. But buried in the report was a sentence that mattered more than anyone seemed to notice at the time: in the previous five years, four other drivers had also passed that same signal at danger. The Automatic Warning System then in use gave the same single warning for caution as for danger, and a tired or distracted driver could cancel it with a reflex. The report recommended that an automatic train protection system be introduced 'without delay,' and that a repeater for the problematic signal be installed in the meantime.

Morgan's twelve-month sentence was reduced on appeal to four months. He served the time and went home to live with the fact of five deaths. Years later, evidence accumulated that the junction itself was the problem - that something about the layout, the sightlines and the signal placement was causing experienced drivers to misread it, again and again. On 12 December 2007, the Court of Appeal overturned Morgan's manslaughter conviction, ruling it unsafe. The court accepted that, as one of the judges put it, 'something about the infrastructure of this particular junction was causing mistakes to be made.' He had carried the legal weight of those deaths for eighteen years. Fifteen months later, in March 2009, Morgan died at sixty-six, drowning in a sailing accident on the River Medina off the Isle of Wight.

There is now a small memorial garden at Purley station, planted to mark the place where five passengers lost their lives on an unremarkable Saturday afternoon. Commuters walk past it on weekday mornings without always noticing. Trains still cross from slow to fast at the same junction, although the signalling and protection systems have changed considerably since 1989. Modern automatic train protection - the kind the inquiry urged so firmly - has spread across much of the British network, prompted in part by Purley and by the worse disasters that followed at Clapham Junction in 1988 and at Ladbroke Grove in 1999. Each crash on a British railway tends to leave behind the same uncomfortable lesson: the warning was already there, in someone's report, in some quiet paragraph, waiting to be acted upon.

It is worth remembering who was on those trains. They were people heading north for the day, into the largest city in the country, with no expectation of being part of anything historic. The 12:17 from Littlehampton was a coastal commuter service that took in the seaside towns of Sussex - Bognor, Worthing, Brighton's southern fringe. The 12:50 from Horsham linked the Sussex Weald to London Victoria. Five of those passengers did not arrive. They were not statistics in a safety report; they were customers who had bought tickets and chosen seats and looked out the window at the Surrey commuter landscape rolling past, the way anyone might. The memorial garden remembers them quietly, in the working pause between trains.