I just drove 200 miles, unloaded the car for 10 minutes or so and then locked it. Came back 10 mins later and tried to start it and just a click from somewhere in the engine compartment and then nothing. Tried to start a few times and the same thing, just a click. Everything seemed to be powered up fine and no battery issues. Got out locked the car and then got in again and it started perfectly.

Any ideas what this could have been?

The intermittent clicking and not starting when the button is pressed was a defective starter motor on my 2012 322, maybe the same on your car. Only Range Rovers since 1988

After only 10k miles! That would be disappointing.

Agreed. If you are still under warranty the easiest thing would be to get the dealer to sort it. In my case the car was 4yo, over 40,000 miles. When they checked it the starter worked, but got unduly hot. It was changed and the problem never occurred again. At that time starter motors went back to LR for refurbishment (and presumably re-use) and one got a credit for the defective unit (not that it would matter if you are under warranty anyway). Only Range Rovers since 1988

There is a switch on the brake pedal that could be faulty.
That's what happened to my Jaguar XFR. Simple fix.