 Exmoor has 55 kilometres ( 34 mi ) of coastline , including the highest cliffs in England , which reach a height of 1 @,@ 350 feet ( 411 m ) at Culbone Hill . However , the crest of this coastal ridge of hills is more than 1 @.@ 6 kilometres ( 1 @.@ 0 mi ) from the sea . If a cliff is defined as having a slope greater than 60 degrees , the highest cliff on mainland Britain is Great Hangman near Combe Martin at 318 metres ( 1 @,@ 043 ft ) high , with a cliff face of 214 metres ( 702 ft ) . Its sister cliff is the 218 metres ( 715 ft ) Little Hangman , which marks the edge of Exmoor . 
