Got a puncture on my commute home tonight - from what I can tell, the glue on an old patch gave way.
Whipped out the tube, grabbed my spare tube and pumped furiously.... nothing.... checked it over - massive hole, looked like it had been chewed! There were some chain links in my saddlebag from where my chain had snapped a few months ago, and I think they had eaten my spare tube.
I didn't fancy a long walk, so I managed to bodge some pressure into the wheel by knotting the tube, stretching it on to the rim and getting the tyre to seat (not easy with 23mm tyres!
Bit of a bumpy ride, and lots of rubbing noises and burning smells, and I got to Epsom station and caught a train home.
Moral of the story, check your spares!