A row of men clutching surfboards stand waist-deep in a sludge-coloured river, buffeted by a chill wind. As a distant roar draws near, they look nervously over their shoulders.
Approaching is the Severn Bore – a tidal surge that breaks up the River Severn before high tide, creating waves of up to 2m. People have been surfing it since 1955, when British colonel Jack Churchill came back from Australia, hopped on a board and gave it a go. But now this very British surfing tradition is under threat, as plans to barrage the River Severn are being re-examined by ministers, who say the tidal surges could provide 5 per cent of the UK's energy. With that in mind, I thought I'd take the chance to surf it while I could.
Having never attempted to surf a river, I decide to consult the expert, Steve King. The 48-year-old, who has been riding the bore for three decades, holds the world record for the longest river wave, standing on his board for a whopping hour and 17 minutes, covering more than nine miles.
The bore won't wait for lie-ins, and it is still pitch-black when I drive into the small Gloucestershire village of Saul where King lives. My headlights pick out an ancient VW campervan and the river king ready for action. We drive in convoy down a single-track road then turn off into the garden of marine surveyor Duncan Milne, 54, our boat driver for the morning.
While most people attempting to surf the bore only get one shot, waiting in the river for the wave and either catching it or not, King has found a better solution: the bore moves upstream at around 10 miles an hour, so with a fast-enough boat you can ride all its best sections in one morning.
Waxing our boards down in the half-light next to the flat brown water, it is hard to imagine this river getting lively, but soon enough the boat is skimming over the water at alarming speed. The sun is starting to come up and in this golden early-morning light even the electricity pylons have something beautiful about them, silhouetted like a row of delicate Eiffel Towers.
Suddenly, the boat comes to an abrupt stop, we throw the surfboards into the water and jump in. Then comes the roar.
I look back and see a ferocious wall of water; it has already scooped up debris and looks so disconcertingly like a natural disaster that I half-think about jumping back in the boat. But I decide to hold my nerve, lie down and paddle. The water hits with impressive force. Within seconds King is on his feet, carving gracefully along the wave. Attempting to follow, I scramble up and immediately nosedive as my board hits the bumps from the currents. Bashing my head on the board as I fall chin-first into the water, I wait to be retrieved by Milne.
I hurl myself up and into the boat like an undignified seal, catapulting myself into the steering block. The next bit of the ride makes the surfing look tame: Milne bounces over the waves until flying through the air to make the final drop of the bore's edge.
I give it another eight or so attempts: each time, I ride on my belly for a few seconds, stand up for a microsecond… then catch an edge and tumble into the water. King, on the other hand, is a master: noticing his hat has fallen off on one wave, he retrieves it with a toe, puts it back on, does a headstand and carries on surfing.
Back in the warmth of King's kitchen, he muses over why he has fallen in love with this very British pastime. "Unlike surfing in the sea," he says, "you can surf along looking at the cows in the fields. There's nothing better." Now the bruises have faded and the feeling has returned to my fingers, I'm inclined to agree.
If you want to have a go, the Severn Bore Inn at Minsterworth is an easy starting point and a great place to watch, as the back-garden has a viewing deck facing the river (severnboreinn.co.uk)
More surf adventures
1. Learn to surf with Stephen Hudson, of Tynemouth Surf Co, in the Victorian seaside town of Tynemouth. He offers kit rental and bags of encouragement for getting in those North Sea swells (tynemouthsurf.co.uk)
2. Cold-water surfing at its most dramatic is found on Vancouver Island. Brave British Columbia’s storms, wade into those big Pacific waves and hang out in the Surf City of Tofino(vancouverisland.travel)
3. Beginners love the consistent waves at Hossegor in south-west France. With plenty of cool camping sites and surf schools, it’s the perfect spot for an easy-going introduction (hossegor.fr)
4. Ride a bore wave created by the world’s highest tides, on Nova Scotia’s Shubenacadie river. There are organised boat trips, though savvy locals use boards or kayaks (novascotia.com)
5. Operators are giving once-troubled Sri Lank the thumbs-up again, and BA is relaunching flights this March. Surfers head for Hikkaduwa in the south-west, with reef and beach breaks plus Buddhist temples and elephant treks (baholidays.com)
6. Surf the waters celebrated in the Bruce Brown film ‘The Endless Summer’. With waves to suit all abilities, Jeffrey’s Bay in South Africa can be paired with a safari (jeffreysbaytourism.org)
7. The Hawaii of Asia, Taiwan offers breaks for all levels of surfer and there’s plenty to do away from the beach, with temple tours, tea plantations, national parks and bike trails (theperfectwave.eu.com)