Took the long way home on the Quota yesterday but partway found that the front brake lever felt odd, somehow. I took it very easy for the next couple of miles and checked the lever once in a while and on one squeeze the lever didn't move - at all. I coasted gently to a stop at a layby and found that the piston in the master cylinder hadn't been returning all the way, so the plunger that linked the piston to the lever had become dislocated and had wedged in the master cylinder. After a few pumps it returned to normal and I carefully trundled home. Oh, well, an overhaul kit is actually the cheapest spare I've bought this year, I think!