Wrynose Pass, climb from the gentle lakeside Greenburn Beck, signs warn drivers: "Narrow road. Severe bends". But if you've come this far, there's no alternative route or turning back. You're about to face a sequence of ridiculous hairpins the width of a bridleway, a constantly disintegrating road surface and unguarded drops plummeting hundreds of feet down the mountainside towards rough moorland, rocks and scree.