Llanwrtyd Wells, in the heart of Wales, is notable for two reasons. It is officially the smallest town in Great Britain, and it is the base for the annual World Bog Snorkelling Championships.

The latter was first held in a dense peat bog just outside our dinkiest town in 1985 and has since gone from strength to strength. Competitors have to complete two consecutive 60-yard lengths of a water trench cut through the bog in the shortest time possible. They usually wear wetsuits — though these are not obligatory — and must use snorkels and flippers. Flipper power is, indeed, the sole means of completing the course; conventional swimming strokes are prohibited.

The World Bog Snorkelling Championship is an international fixture, attracting coverage from Fleet Street's finest every August bank holiday. Every year, when I read of it, I cannot help but wonder what on earth would possess anyone to swim — sorry, flipper — through a bog. Still more bewildering is a sister event, the Bog Snorkelling Triathlon. This is as deranged as it sounds: entrants run for 12 miles up and down Welsh mountains, complete the standard bog snorkelling course, and then cycle 25 miles. Those events on their own are ardous enough — who would want a festering bog thrown in?

Wendy Brown is a 39-year-old clinical risks associate with Beachcroft LLP, a mother of two small children and an amiable, outgoing sort. She is also a bog snorkelling champion.

“My colleagues think I’m completely crazy,” Brown says. When she returned to work after the event, “there were a few jokes about whether I’d had a shower. I assured everyone I had. In fact, I even had a change of some clothes, at least, for the cycle ride. I didn’t want to do it stinking of bog.”

Quite right. But why go bog snorkelling in the first place?

“I’ve always been into triathlon and keeping fit.”

Brown studied for her Law Society finals in Bristol after completing a law degree at Birmingham University. She now works from Beachcroft’s Bristol office and remains a keen athlete, helping to set up the Bristol and District Triathlon Club. But her sense of imagination, not to mention humour, drives her to events that, depending on your point of view, are either eccentric or barking mad.

“I’ve competed in the Bristol Rat Race,” she says, an event that involves kayaking while blindfolded and running over the bottoms of boats in Bristol harbour. Brown also intends to compete in the Great Gorilla Run, in which participants run a four mile circuit in London dressed in a gorilla suit. Both, though, seem positively soft compared with the requirement to snorkel in a stinking bog.

“I’m drawn to the more eclectic events," she confesses. "As a triathlete, the idea of combining World Championship bog snorkelling with running and cycling was irresistible.” That was not easy. “Quite a few people struggled and the various disciplines make for a tough course. The bog is pitch brown and the only kind of swimming stroke you’re allowed to use is doggy paddle. It’s a really narrow trench but I managed to overtake someone and came third in the women’s category overall.”

The good news for anyone entering the event is that, irrespective of where they finish, bog snorkelling custom and practice entitles them to describe themselves as a World Champion. Brown embraces this aspect of the sport, for as she says: “How many other sports can you enter as an amateur and come out the other end being allowed to call yourself a World Champion?”

As to the allure of bog snorkelling: “It’s just so funny. And so silly.”

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