Last Christmas holidays I stood on a point of great significance in the geography of Britain. The summit of Sgurr nan Ceathreamhnan (that’s approximately Skurr nan Kero-anan) at the head of Glen Affric with grid reference NH057228 is precisely on the watershed of Britain. Water falling to the west of the summit goes over the falls of Glomach and runs to the Atlantic at Dornie. To the east all the rivers drain into the River Beauly and into the North Sea at the Moray Firth. The watershed forms the source of a number of interesting problems at various levels of difficulty.