Defrosting in front of the computer, after agency-approved locksmith turned up, decided the lock didn't take Mastercard and re-attempted my jibble-it-through-the-letterbox approach using a Mk1 coathanger and a mirror instead of two spokes and some gaffer tape. He didn't get it to work either, but I reckon I won that round on account of not dropping my burglary tools through the letterbox.
Locksmith eventually gained access using a drill and the now legendary Bigger Hammer, and we are now the proud owners of a shiny new Yale lock that isn't prone to self-deadlocking due to vibration, and a small pile of splintery wood.
Only rode 1km in the end, so no verdict on the knee other than it's a bit cold.
I think it's just stopped raining.