He returned to Formula One in 1977 with his own LEC chassis designed by Mike Pilbeam and run by Mike Earle. It was this car in which he suffered serious injuries in an accident during practice for that year's British Grand Prix. He survived an estimated 179.8 g when he decelerated from 108 mph (173 km/h) to 0 in a distance of 26 inches (66 cm) after his throttle became stuck wide open and he hit a wall. This was the highest measured g-force ever survived by a human being (until in 2003, Kenny Bräck's crash violence recording system measured 214 g). Purley suffered multiple fractures to his legs, pelvis and ribs.