Weeks passed and nothing happened so I decided to enlarge the hole. Again, I did it carefully and made the hole a little bit bigger. Then I thought, 'I know, I'll get a fan heater, blow some hot air through the hole and see if I can't drive out some of the condensation that way'.
After thirty seconds of that, of course - ping! - the window cracked.
I cursed myself for foolishness and then sat around in a funk.
Soon bored with funk, I thought I'd go out and do a bit of shooting. On my way out of the flat I propped my bagged rifle up against the door frame while I grabbed my jacket and - bugger! - it promptly fell to one side, straight down onto the scope, bent the 50 millimetre end-lens housing out of true and cracked the central tube.
So, the scope's on E-bay, I'm on the look out for a nice, tasteful window sticker and I've gone back to shooting with iron sights.