Took a short trip this morning, stopped the car, exited & locked. Returned a minute later unlocked, key in, clutch down starter pressed; got a half hearted turnover (this happens sometimes & I think it's because I haven't depressed the clutch sufficiently), tried agin & nothing, tried three or four more times, removed the key & tried reinserting, still nothing. Eventually I got out, locked, unlocked & tried again & this time it started normally. Any ideas?  From a time when dinosaurs weren't just confined to zoos!

Ideas could be many, but the real cause could be different than any of them.

The clutch switch is an on/off one. Either is allowing you to start or not. There is no in between like turning half revolution because you didn't press it enough. So, if this happens sometimes, could be the symptom of the real problem.

Ideas.... The starter motor or its power supply circuit.

I see you have a 2010 TD4 e which should have 2 main earth leads. Double check both earth leads (battery to body and battery to starter motor) for good connections and no corrosion. Ensure there is no corrosion under the crimps of the terminal fittings. If you can, get them checked for high load resistance. Notorious area for random faults. 10MY (Sept 09) TD4 HSE Auto in Stornoway Grey (Now Gone)

08 FL2 TD4 SE Manual in Rimini Red (Now Gone)

I had this exact problem a few weeks ago. Bought a repair kit on ebay which contained a new starter solenoid and contacts for the starter. Fitted, and no problems since.

Jon.