A39 Exmoor — Watchet to Ilfracombe, Somerset / Devon

Distance: 44 miles (Watchet to Ilfracombe via Porlock Hill and Lynmouth) Altitude: 1,141 ft (Porlock Hill summit) Max gradient: 25% (Porlock Hill, steepest A-road in the UK) Best for: Coastal moorland touring, dramatic climbing, southwest England adventure Best time: April to October