I had to fettle a new inner tube onto the front wheel of the Kaffenback, which went down overnight. At least it happened today, when all it did was delay me a bit going to Sainsburys. If it had happened tomorrow morning, I would have been annoyed.
I buggered around for a while trying to find the cause, and eventually realised that the valve was slightly coming away from the tube, which was unusual. At least it meant that the Marathon Supreme tyre wasn't to blame, and could keep it's good record of virtually no fairy visitations.