Bugger, bugger, bugger!
It's clear that I'm too old and too inept for this off-road lark. Yep, as the guy from Worthing on (actually off!) the Adventure, I managed to make it home, took off my boot and the ankle ballooned up. So, off to A&E where the X-ray showed - a broken ankle.
I've cleaved a triangular bit off the fibula (smaller bone) just above the main anke joint. Temporary splint at the moment, fracture clinic tomorrow, where the orthopods will decide whether it needs surgery to pin the bone, or just plaster it and leave it. Either way, it's 12 weeks in plaster.
Many thanks to all those that helped - particularly the guys who rode my bike to the road and gave me a pillion. Much appreciated. What a pity it ended that way as it was a great day out - lotsa fun and a great bunch of guys. Thanks to Steptoe for organising it - looks like a new(ish) bike is stronger than an old(ish) bloke!