Is that the brassy coloured thing that sits inside the follower?
if the timing belt has slipped due to iffy tensioner or just worn....then it can knock out the cam timing which can cause piston and valve to meet....
Have ordered new rod, new followers and brass thingies, timing belt, tensioner, front gasket, water pump gasket, crank oil seal.....
So will strip the top end down and take the head off while I await delivery, fit the new guides and seals and then fit new followers, do the timing belt and tensioner etc and see what happens.
photos and write up Ant?
Of course....will be posted in the Defender section obviously!