Caving: ‘The last true UK wilderness’

The 23 -year old, who is a member of Exeter University’s caving club, describes another caving technique called a “squeeze”.

“It was a long crawl on my belly with cave walls only inches from my body above, below, and beside.”

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Image caption Some caves have chambers large enough to fit a cathedral, while others are a narrow squeezing, the British Caving Association says

Image caption Mr Sewell, here discovering a cave in Northern Ireland in 1996, hails the “amazing” feeling when you are one of the first humans to step into a cave

Image caption Exeter University Speleological Society runs day and weekend trip-ups, often to nearby caves in Devon

Image caption Mark Fox, who started caving 20 years ago, tells the thrill comes from “the opportunity to see things not many people have”

Image caption Ari Cooper-Davis, from Exeter University’s caving club, says he was “a little bit scared” before trying caving for the first time

Image caption Chris Binding describes underground as “an unusual natural world” with “geology you don’t usually see”