More a case of 'what I didn't do with my RR today' - I didn't lock it.
Went out with the dog this morning and on my return noticed that the mirrors weren't folded in and sure enough, the car is unlocked. Ok, that's unusual for me but not unheard of. Grabbed the keys and pressed the lock button, nothing. Hmm, is the battery flat in the key? No, if I press the unlock button it pulses the locks, headlights, boot release etc. all working just fine. Even more curious.
Resign myself to the fact that I have a faulty key button then, that's a shame. Grab the spare keys and guess what, yep, won't lock. All other buttons are fine.
The keys must be fine from a coding perspective. Never seen this behaviour before. I'll try starting and driving it at some point to see if it recovers at all or some kind of reset may fix it but if any of you have had this I'd be interested to know what might cause it.