Caporegime
The Williamson incident was the worst, as he could have so easily been saved. The sight of the marshals standing and watching David Purley trying to save Roger is sickening. Williamson wasn't even injured - he suffocated.
It was a truly horrible incident but I think it's a bit unfair to blame the marshals: Purley was the only one in fireproof clothing, the couldn't get close themselves without being horribly burnt.