They wear protective clothing for a reason – but these cavers are braving it in the buff to raise money for charity.

Amateur photographer Laura Brown, from Highgate, has taken underground exploits to another level with her Bare Naked Caving 2013 calendar, shot at 13 locations across the country and in Paris.

All profits from sales of the calendar will be donated to cave rescue teams in Wales and Yorkshire.

Navigating cliff faces and deep, dark caverns is difficult at the best of times, but carrying heavy camera equipment and lights brings extra challenges.

“Sometimes I couldn’t get the right shot because the conditions were too challenging,” explained Ms Brown, who said there were some harrowing moments during the shoots.

The 29-year-old, who works as an analyst, said: “One guy who’s a climber took all his clothes off and climbed half way up the wall, but I couldn’t get the shot so I told him to come down because it was too dangerous. Another female member was suspended from a ladder for 20 minutes because I couldn’t get the shot.”

One of Ms Brown’s favourite photos in the calendar is of two male climbers casually eating breakfast on top of a steep rock face overlooking a valley.

The moment captured at a unique vantage point was one the photographer wanted to include in the calendar, along with more serious depictions of man versus nature.

“I liked the idea of the human form naked in a cave in harsh surroundings, but I also wanted to raise some smiles,” she said.

But the climbers were not the only ones to strip off, Ms Brown also shed her clothes to stand naked in front of the lens.

“I felt nervous at first but we’re all close friends and because you’re in a cave, it removes you from the reality of the situation, and you do feel quite liberated,” she said.

“It being dark helped as well.”

Caving is a rare hobby when you live in a city, but it was one Ms Brown could not resist when she found the Westminster Speleological Group, a London club devoted to caving.

With 30 active members, the club goes on trips all around Europe to find the deepest of caverns, complete with underground rivers and hidden tunnels.

But it comes with some serious risks.

Ms Brown said that being caught under a waterfall is the most common cause of disaster, and she once had a close call when she got stuck on a rope, amid freezing cold, gushing water.

“Getting too cold in a cave because of an incident like that has been a cause of death for many cavers and a reason why Cave Rescue is so important and why it is so vital that we support them,” she said.

The calendar is on sale for �10 at Bare Naked Caving.