[G-CPTN]

This describes when a driver climbs a steep hill in a low ratio gear then 'coasts' down the other side (not in neutral, but by 'simply' depressing the clutch whilst remaining engaged in the low gear).
As the vehicle speed increases, the propeller (drive) shaft drives the gearbox and, in turn the clutch driven disc (which, being unclamped, 'bursts' as it reaches rotational speeds way in excess of its 'structural' strength and throws off the friction linings). Of course, especially in the case of a 'pot' type flywheel, the pieces jam between the pressure plate and the flywheel so the driver discovers that he is subsequently unable to declutch.
It might be a phenomenon that is specific to test hills rather than normal transport operations (we had several severely steep gradients, though each had a suitable run-off area in event of brake or transmission failure).
At least one driver engaged a low gear in anticipation of descending a steep gradient but let the vehicle roll with the clutch depressed, gathering speed until the clutch burst - then claimed that he had done nothing wrong . . .

Subsequent stripping of the transmission proved him wrong.

That's all, folks. Have any of you had engine or transmission failures leaving you disabled en-route?