All good guesses I guess - but I suppose I should put you out of your misery. The hint was that the original builder was a complete pillock ! Believe it or not this is the remains of a crankshaft spigot bearing - machined out of nylon !!When I first found it, it was one of those moments when you just can't believe what you are looking at. As you can see, as it melted it spread itself past the the flywheel bolts and left a very pretty flower-shaped piece !The amazing bit was that it lasted nearly 200miles. Obviously,to the bird-brain who did,it must have "seemed like a good idea at the time", but I struggle to understand how anyone, nevermind a FI technician, could have contemplated using a thermoplastic material.I hestitate to name the individual reponsible, but I am aware that he worked for a, now defunct F1 team, and also of a horrible accident, badly injuring one of it's drivers, caused by a mechanical failure.I can only speculate on whether there is any connection the aforementioned pillock.