The turbo shaft is seized solid!

Any ideas as to cause of this? I change oil regularly - castrol RS. Never thrash it when cold, always let it idle for 20-30 seconds after a good thrashing.

Gutted.

If i take the oil feed off top of turbo and start engine will that be good enough proof it was getting oil? Should i attempt to start the engine with the shaft seized as it is?

Cheers