In hindsight, our mistake was cycling down the towpath, which runs alongside (the canal!) long-thorned hedge bushes. That have recently been trimmed, causing sharp-thorned debris to fall onto the towpath.
Tis often said that the secret to good comedy is timing, and the punctures came along with perfect timing.
RC got the first puncture, and we all stopped while she stripped the wheel and replaced it with the always-carry-a-spare tube. She had just about finished when the Sparkly One noticed that her front tyre was flatter than it should be.
Chuckling quietly, I set about fixing it and in short order had installed the spare tube. I was just pumping it up when, with a slip of the wrist, I snapped the valve off in the pump - rookie error! The tube was beyond repair, useless. And I had no other spares, no repair kit.
Several moments passed during which all of the most severe curse words were invoked. A small child, passing with his family on their Boxing Day stroll, almost went blind at the language. Two small birds died instantly. The inner tube remained useless.
DB had already spotted the predictable flat in his own rear tyre and begun replacing it. We did a quick swap of tubes - he patched The Sparkly One's original for himself, having been wise enough to bring a patch kit - and I fitted his replacement to her bike.
Finally, when we were all just about ready to set off again, I spotted the flat in my own rear tyre, and set to fixing that.
I told you, comic timing.
At this point, we were agreed that the Stars Were Not Right, and laid a plan to head home by walking our bikes to the nearest road, and cycling straight home. As we set off, DB got the fifth puncture of the day. He fixed it in grim silence.
Repeat after me: always always always carry a spare tube, and a puncture patch kit.