The climb to St. B. was uneventful, if somewhat rough at times, until lock 19. There, despite the fact that MWNN had the front AND centre ropes, the boat took off at speed and crashed into the opposite lock wall with force. The shelves in the galley flew out, depositing their contents on the floor, the bookcase collapsed and the cupboard containing CDs, radio, camera, and other electronic devices crashed open. Anyhow, I was on the tiller throughout and, as the boat took off, the force of water caused it to heel over to port to an angle at which the threat of 'turning turtle' is a real possibility. MWNN was worried that the impact with the lock would catapult me off the back deck, over the semi-trad sides. As this was a relatively shallow lock (less than 3 metres) we didn't see the need for life jackets.
MWNN complained to the lock keeper, to no avail. As I suspected, it was our fault for not tying the ropes tightly round the lockside bollards. MWNN's French becomes fluent when he's angry and he let the lock keeper have both barrels of ire, explaining all about the dangers of compression knots as the boat rises above the level of the bollards, our experience of over 3000 miles of French waterways, and 10 years experience of handling our own boat.