Button marked "P" where the switch to control the convertable roof is. What the hell is it?

Sure, the most obvious answer and one at which I have no success. The trouble with the XK's manual and probably all manuals, is that you need to know what it's for to look it up in the relevant section. I've ploughed through everything and probably missed it when I was glazing over with the welter of different ways to achieve the same thing. There's a nice photo of all the controls and captions of what they are and what they do. Unfortunately the photographer's camera didn't include this control up at the top of the windscreen. So, I'm not looking for the easy way out, I genuinely don't know where to look and the dealer is a bit of an arse.

Sorry, didn't respond to "what happen if push button". Seems to me that's a bit like finding a bomb outside the front door and saying "what happens if you touch the two wires together".

‘Full’ index is in back of book. I doubt it’s going to explode! Perhaps someone with ‘like vehicle’ will respond - - Good luck.