Eventually found this about it:
"The European jockeys’ practice of ensuring racing room for themselves and their rivals may well owe much to what is by now a folk memory for many of them - the 1962 Derby, the first of Vincent O’Brien’s record seven successes in Epsom’s Blue Riband. With so much at stake, the Derby does produce an undue amount of tight riding, bumping, boring and jostling, accentuated by Epsom’s unique configurations.
Halfway down Tattenham Hill, obscured from grandstand viewers by the huge throng on the rails and also out of shot for the television and patrol cameras, it subsequently transpired that Romulus, ridden by Wally Swinburn, had clipped heels and come down. Hethersett, the favourite ridden by Harry Carr, got caught up in the faller’s legs and also came down. They were followed in rapid succession by Pindaric, Changing Times, Persian Fantasy and King Canute II. Remarkably, Pindaric proved the only fatality.
Australian Neville Sellwood could hardly believe his luck, Larkspur having jumped the fallen Romulus before running out an easy winner. Moreover, he had not even been Vincent O’Brien’s first or second choice of rider, only booked when a number of other jockeys had declined the mount for various reasons. Sadly, this genial jockey’s luck turned tragically at Maisons-Laffitte that November, when he suffered a fatal fall."
from:
http://www.carlow-nationalist.ie/tabId/380/itemId/4826/Old-jockeys-never-die.aspx