Couple of weeks ago, went to get into Tri & noticed a piece of dark heavy wire on floor.
Closer inspection it looked very much like a piece of broken spring.
Grabbed a torch & had a look around pedal arm area
1/2 of the clutch pedal return spring is missing.
Mystery solved.
It is being replaced after Christmas under warranty. Was obviously poor quality spring steel to break like it did.
ML 3.2, 2009 model. 19k on clock.
I have done a search & cannot find anyone else with similar problem.
Might pay to keep an eye on it if you have similar model. I don't know if it was a one-off or a bad batch.