So there I am on the home leg of my commute carrying 2 spare tubes, spanners that fit 99% of the nuts on the bikes, allen keys to fit all the right sizes, a frame pump, tire irons, and a patch kit. "Enough for any problem" I think. Then the crank falls off and the nut rolls off into the void. Of course, if I had been carrying a socket wrench and the right size socket (which I have from last bike... at home at the time) this wouldn't have been the 10km walk of shame that it became. Sigh, unless you carry a whole toolkit I guess you can never be prepared for everything.