There was very little visibility on the course – at least in the swimming section – when the Rude Health Bog Triathlon was held at Llanwrtyd Wells in Wales on Saturday.

The event, one of the most unusual in the triathlon calendar, has been running since 2005 around the Waen Rhydd Bog, which is well-known for hosting the annual World Bog Snorkelling Championships.

The triathlon sees individuals or relay teams of three run for eight miles before swimming a single length of the 60-yard peat bog trench. They then force their tired limbs on a 12-mile mountain bike ride.

The course will be reset on Sunday for the World Bog Snorkelling Championships, a charity fundraising event which has been running since the 1980s and attracts hundreds of spectators.