It is usually around Junction 17, heading south-west on the M5, that you begin to notice it.
Like a rooftop contagion, every other car seems to have sprouted a surfboard or three. Some have hastily tied straps flapping against them; others are piled up in minivans ready for imminent use, and the shorter ones nestle next to a proud owner on a reclined front seat. As the main gateway to the popular surfing spots of Cornwall and north Devon, the M5 can often feel like a pilgrimage route on a Friday evening as hoards of the desk-bound make their way as fast as possible towards the sea.
But it wasn't always like this.
What began as a hippie pastime of the 1960s – enjoyed by a few hardy, young beach bums in ill-fitting wetsuits – is now hardly recognisable.
While previous generations of local pioneers bobbed about on oversized planks in twos and threes, today an estimated 250,000 people in Britain go surfing every year.
If there's a beach with a wave, it is safe to bet it will be packed.
This weekend sees the conclusion of the biggest event on the UK's surfing calendar: Newquay's Boardmasters, with more than a hundred thousand people coming from all over the country to watch surf contests alongside big name bands.
The six-day festival and competition, which is estimated to bring some £17m into the local economy, is a perfect example of how surfing in Britain has gone from quirky hobby to multimillion pound industry.
And the contest shows just how much Britain has put itself on the global map for surfing, with competitors from South Africa, Brazil and Australia all coming to compete for the $120,000 (£75,000) prize money.
As part of the Association of Surfing Professionals' World Qualifying Series, points scored at Boardmasters could propel a surfer to a coveted place on the world tour – the surfing equivalent of the Premier League, which has just 46 men and 16 women competing in the world's ten best surf spots over a year.
Russell Winter is the first (and only) British surfer ever to make it on to the world tour. The 34-year-old is still Britain's number one and is currently leading the scoreboard at Boardmasters, the first heats of which started at Newquay's Fistral beach on Tuesday. He started surfing when he was nine years old, after his family moved from London to Newquay, and says that – unlike when he started out – you now see many more people coming from elsewhere to surf. "Surfing is definitely getting bigger, which is not so good when there's a crowded line-up, but it's great to see people out enjoying it. I think the internet has had a lot to do with making it more accessible to people in cities.
"You can watch the professionals online, but it also means you can check what the swells will do, so you can be sure there's going to be waves when you come down."
Websites such as Magic Seaweed, which has simple charts forecasting wave size and quality around the country, have completely changed the way people surf. Instead of driving hours from a city to the beach only to find the sea appears to have been ironed flat, now people can log on and decide whether the conditions look worth it. While this bypasses the more complicated pressure charts that used to be available and is great for those living a long way from the surf, it can be a source of frustration for the locals, who now have to share the great waves with the hordes.
I am one of a growing – and sometimes loathed – clan of surfers in Britain with no local beach. I have never lived by the sea; in fact, growing up in Oxfordshire, I could hardly have been further from it; I work full-time in London and, aside from ironic references, I'm pretty sure I have never said "dude". Yet I find myself several times a month hurtling down the M4 and the M5, just for the pleasure of waking up the next morning next to waves. Ditching my compact city car in favour of an oversized van called Mave, I have now honed that process – often falling asleep in clifftop laybys at 4am so I can roll out of bed and into the sea.
The huge demand to surf has created its own market. Big Friday is a company that was set up eight years ago by Kate Czuczman and Rhona Gardiner, two city-locked surfers who wanted to make the schlep from London to the waves easier. They started out with just a handful of trips but now their bus is out most summer weekends, picking people up in west London and dropping them at a pre-arranged lodge in Newquay.
The company has now expanded to arrange surf holidays for Brits all over the world, from Costa Rica and Bali to Spain and Morocco. Ms Czuczman believes part of their success lies in how easily people get hooked on the sport. "It's very addictive, there's that classic catchphrase 'only a surfer knows the feeling' – over the years through running Big Friday I have seen lots of people take up surfing and watched it change their lifestyles in a really positive way," she says. "We have lots of repeat guests and lots of people that learn to surf with us in the UK then venture abroad with us."
Many of those who surf now are not drop-outs, nor are they all muscle-bound beach jocks. As the sport becomes more accessible in Britain, those picking up a board often fall into that estate agent-favoured category of "professionals".
Attracted by the outdoor lifestyle, the adrenaline rush and the simple pleasure of being pushed around by nature, people are prepared to spend money on the journey, equipment and accommodation. Most of the friends I have made through surfing – including civil servants, a policeman and an army officer – could not be further from that founding counter-culture but they all share an enthusiasm for the sport.
Speaking over the din of the contests from the British Surfing Association's offices on Newquay's Fistral beach, operations manager Joanne Hillman says there has been an explosion of interest in the sport.
"There's always people learning to surf, but over the last couple of years it's had a really steep growth. We did a survey of members, and a lot are people who tried surfing when they were students and are now professionals who go surfing a few times a month. It's not just blonde-haired, dreadlocked surfers living out of campervans and washing dishes; in the last ten years a lot has changed."
Roger Mansfield, author of The Surfing Tribe, a history of Britain's board riders, says he has noticed a cultural shift take place in the 47 years he has spent surfing in the UK.
"It's been incredible. In the last 10 years what's been noticeable is the number of people turning up and treating it as a recreational sport like any other. That esoteric surfing culture that was just one part of society has gone. Now grandparents down to babies have wetsuits, and all hit the water."
Mr Mansfield believes surf schools may be partly responsible. "Since I started the Offshore Surfing School in the late 1970s – which was then the first surf school in the country – the surf school phenomenon has really boomed. They treat surf school the same way as people treated ski school and it all adds to this sense that it's a sport anyone can do."
While Newquay locals like Mr Mansfield have seen perhaps the most dramatic invasion, across Britain, from the massive, barrelling waves of Scotland and Northern Ireland to Wales's spectacular Gower peninsula, more people are grabbing boards and heading into the sea. Even Kent – known more for bucket-and-spade holidays than its "gnarly" rollers – has its own surf scene.
The north-east is also a surprising surfing hub, with some of Britain's most perfect waves to be found near Hartlepool, Redcar and South Shields. The growth of the sport in such places is partly attributable to modern wetsuits – as they have got cheaper, lighter and more flexible, they have made braving the North Sea slightly less foolhardy.
Meanwhile, the locations of some of the best "secret spots" remain ever-more closely guarded, as a wave of surfing guides to Britain has "outed" many. Until recently, one such spot was Broad Bench, a flat slab of rock in Kimmeridge Bay on the Dorset coast, which produces world-class waves when the conditions are right.
But the waves break right next to a Ministry of Defence (MoD) shooting range, and over the years access to the water for surfers has been limited to a fraction of the year. Campaigners were faced with the dilemma of keeping their prized wave a secret or risking getting to the point where nobody was allowed on the restricted beach.
Bournemouth-based Guy Penwarden, 51, who has been surfing "the Bench" for 40 years, has been leading the battle against the MoD. "There's always that sense of not wanting to encourage the crowds but we had to bite the bullet or nobody could surf it. It's absolutely unique and one of the best waves in the UK."
Protecting waves and access to them has become the latest cause célèbre of Surfers Against Sewage, a group which, as its title suggests, came together to campaign for cleaner waters. This week they launched their Waves Are Resources report, justifying the need to protect waves for surfing using hard economics.
Economics may have been anathema to the surfers of the 1960s and 1970s, but now even local councils will spend millions trying to court the surfing pound. It is an irony not lost on Mr Penwarden that the naturally-formed Broad Bench is exactly the kind of wave that engineers had been trying to achieve with Bournemouth's sub-standard £3m artificial surf reef just up the road.
The reef, which a recent report concluded made "the wrong kind of waves" because they were too short and too infrequent, was made to attract more surfers to the town.
But for Bournemouth surfers like Mr Penwarden, more crowds are not necessarily what is wanted. The risks involved are now as much to do with other surfers as the sea itself.
"It's definitely getting busier; at times it's a bit like switching the traffic lights off at rush hour – people need to learn the rules. It's an accident waiting to happen."
With overcrowding, those who live by a great wave can resort to extreme measures. So-called localism – defending your home surf spot – is occasionally found in the UK. "I've seen localism in Cornwall and Devon – it can get aggressive" Mr Penwarden says.
"I've seen people writing in wax on people's windscreens and tyres slashed. I hear so many people complain about crowds, but you have to share these things. I've had a great life out of it and still do, so I think more people should do it. Everyone wants to surf with no one else around, but that's not going to happen anymore."
Being more popular has its upsides, Mr Penwarden says. "I remember being in my town and people laughing at me for surfing. It was like seeing someone skiing up the high street, so of course someone was going to take the piss. They would throw stuff at me from the pier. Now people realise how much fun it is."
Tickets for Relentless Boardmasters 2010 can be bought at www.relentlessboardmasters.com