As a guidebook writer, Harold Drasdo wrote the first Fell & Rock Climbing Club guide to the Eastern crags of the Lake District in 1957. In 1971 he became the first climber to write both English and Welsh guide books when he wrote the Climbers' Club guide to Lliwedd. As a consistent explorer of undeveloped crags in England, Wales and Ireland, he has established many first ascents, including North Crag Eliminate (E1 5b) on Castle Rock of Triermain, Grendal (VS 4b) in Deepdale, Anarchist (HS 4b) on Raven Crag, Ulysses (VS) in Donegal, Automedon (VS 4c) and Heart of Darkness (VS 4c) on Arenig Fawr, and Traditional Route (S) on Craig Rhaeadr Ewynnol.