Driving up the Llanberis Pass on a grey afternoon, my eye was caught by a group of young people gazing intently at one of the huge roadside boulders near Pont y Gromlech, and I pulled into a layby to watch them at their sport. They belonged to the rock-climbing sub-sect of “boulderers”, and were focused on a leaning wall of pocketed rock perhaps five metres high.

Clothed in T-shirts and loose trousers, with sticky rubber rock slippers on their feet, they had chalk bags strung round their waists, and thick foam crash mats laid out beneath the wall. Each in turn stepped to the base of the wall and went through a set of mimetic gestures anticipating the moves to be made above. They felt at the initial holds, arms taking their weight, toes stabbing at edges and pockets that might afford some lift, then flopped more or less elegantly back on to the mats beneath.

Bouldering has a long history here. The problem engrossing this group was first solved by a pioneer from the 1930s, John Menlove Edwards (1910-58) – who remains the finest and most psychologically acute of all essayists about climbing. He ascended it in hobnailed boots and an old Fettes school blazer. Thousands have done it since, their ascents imparting a fine, discomfiting sheen to the holds leading out across the wall. These days it’s known as “The Ramp”, and given the relatively lowly grade of five in a system that now stretches into double figures. But it still has historic as well as sporting interest, still makes your muscles work for victory. None of the aspirants reached the top while I was there. Maybe the silent, watching presence of an old codger put them off?

So I drifted across the road and talked over a wall to a Sikh family – the women hospitably inviting, the men affable – sitting on a rug by the stream and enjoying an elaborate, aromatic lunch. The climbers still persevered. Their mouths must have been watering.

I peered into the cave under the boulder. Legend has it as the home of a child-eating hag, Canthrig Bwt. If her appetite was being stimulated as much as mine by the Sikhs’ banquet, the boulderers standing within reach of her lair had better be quick.