Hi Damian,
Well this last photo tells a bit more of the story. It's amazing what some unlearned people will do. Tools should be operated by people with licenses I always say.
As John Cleese once said, a Bee License, a Fish license, I say a tool license.
Anyway from where I'm sitting I feel it's because the clutch was poorly adjusted originally by an unknowledgeable person and the fibre washer has been worn away to nothing and as such the brass has been gripping with uneven pressure onto the cast iron of the cone which is generating heat that's being passed on to the fork. (not helpful) I'd say that someone has just kept on applying more pressure on the adjuster screw as the brass thrust pad kept wearing away (as can be clearly seen) and inevitably the fork has had enough and failed.
Cheers,
BB.
