A local train stood at the Harrow and Wealdstone platform a few minutes after eight, full of people going to work, when the overnight express from Perth ran into the back of it; a third train struck the wreckage. One hundred and twelve people were killed and three hundred and forty injured, among them the crews. Doctors, nurses, railwaymen and American airmen from a nearby base worked the site for sixteen hours. This was 1952.
The American unit from South Ruislip set up a casualty post at the site and sorted the injured by severity before moving them, which was still unusual practice in Britain then. They also had plasma and penicillin to hand. Several of the methods used that morning fed into later civil ambulance planning.
The inquiry that followed pushed the fitting of the automatic warning system onto the main lines at a pace it hadn't had before; it had been trialled for years, and after Harrow it moved. Small comfort to the families, but it did move.