Many thanks for the helpful comments. Much appreciated.

We were almost certainly sailing too slowly. Our beach is in a small bay with ferry traffic. To avoid a ferry we'd been forced to sail into the wind shadow of the windward headland. So we'd slowed down a lot. Possibly a slight gust hit us from around the other side of the headland, too.

If we get caught again in the same situation, I'll do an S-gybe or perhaps for safety just luff up, tack, and bear away instead. But above all we'll try to avoid the situation by keeping the spin up and sailing fast right into the bay.

Agree that speed is your friend. One of the first things I was told when I started sailing the F18 was that the faster you go, the safer you are. Opher's coined a good warning: Not too low, not too slow.

On a related topic: I reviewed Georges Tillard's Catamaran Sailing DVD last night and noticed that it recommends easing the main a bit during a gybe and then trimming in again after. I wasn't taught to do this and wonder if others regularly do it or not. (I was taught "Keep the main tight downwind, it's your backstay.")