Slippery runway
As one who was at Thorney in 1968 working on the Farms dispersal on Hec 1st line I remember the incident, however the slippery bit refered to at the ends of the runway was in fact a low friction coating applied to reduce rubber build up from the Hercs on touch down as the constant circuits involved in the training resulted in heavy wear on the mainwheel tyres and consequent buid up on the threshold. Watching the Dead Sparrows going in all directions after a fast taxi on the runway did provoke a smidgen of mirth from the watching crowds!
In a later life I spent several trips as a G/E on the Herc taking both the Gnats and the Hawks round UK and Europe, my strongest memory being loading Palouste starters onto the ramp of the Herc whilst they were still rather warm! Flight Safety read and weep!