The perfect wave: Surfers' holy grail at risk

It is Britain's best kept surfing secret – the UK's perfect wave. In ideal conditions, at a closely guarded offshore location, a 15ft wall of water barrels its way towards the coast, forming a smooth tunnel that can be ridden by skilled surfers for minutes at the time – the most coveted goal in the sport. Aficionados claim the spot rivals some of the best surfing waves in Australia and Hawaii and has been used to help hone the skills of some of Britain's best surfers.

The precise location of this holy grail of waves has been known by only a few, who have kept it to themselves fearing that its unique qualities could be spoiled if it became widely known – until now.

The wave, dubbed Broad Bench, comes ashore at Kimmeridge beach, on Dorset's Jurassic Coast. Dorset surfers decided to reveal the big wave's existence because the Ministry of Defence, which owns the beach closest to where it breaks, is restricting access to it. One surfer described the MoD's actions as like "telling a climber they can't go up Mount Everest".

The surfing holy grail is close to the army's Bovington and Lulworth training camps, and increased use of nearby shooting ranges has prompted the military to close the beach to the public for most of the year. The MoD's move has angered irate Dorset surfers, who then decided to reveal its location in a campaign to allow them to ride it freely again.

Launched today, the online campaign, known as the Access Broad Bench Association (ABBA), is being led by Guy Penwarden, one of the UK's best surfers. Mr Penwarden says that learning to surf on the wave meant he was able to compete at an international level. "It's a holy grail in British surfing: a bigger, hollower, and longer wave than any other in England. It's far more challenging than anything in Cornwall, and we've even had visiting Australians say it's as good as anything they have ever surfed out there," Mr Penwarden said.

Until now we didn't want hordes of people turning up, as it would have ruined our relationship with the MoD. But now that they're hardly letting us out there, we want everyone to know about it."

The only time surfers are now able to access the beach is on selected weekends. But even this is now under threat, as fears grow that the Army's movement of more training facilities from Germany will result in a total shutdown. As the wave only forms when the swell conditions are right, surfers often have to watch in disappointment as perfect waves in the week peter out to a flat weekend.

Dr Tony Butt, an oceanographer who is also one of the country's premier big wave surfers, said the peculiar geology of the Jurassic Coast had created a near-perfect flat rock for the long "tube" waves to form.

Steve England, associate editor of Carve Magazine, said that surfing insiders have known about the break for decades, but had kept it confidential to stop it being swamped. "It's one of the best waves in England, and it's also one of our best kept secrets. It's the jewel in the crown of the south coast and yet most people haven't even heard of it." He said its loss to British surfing could be catastrophic.

An MoD spokeswoman said the move was perfectly legitimate. "If the beach is on the Defence estate, then clearly that's what we're using it for," she added.