They line the banks of the river in the picturesque Oxfordshire town of Henley-on-Thames, hundreds of spectators are dressed for one of British summer’s most prestigious social occasions.

The ‘ladies’ — because that is what they are referred to in these parts — are clad in long, flowing dresses and extravagant hats; the ‘gentlemen’ in striped blazers, straw hats, smart ties and deck shoes. Only in extreme heat are they permitted to remove their jackets. And amid the hubbub of cut-glass conversation, the popping of champagne corks and the glug of Pimm’s offers a distinctive soundtrack to a very different kind of elite sporting competition.

This is Henley Royal Regatta, the world’s most prestigious rowing event. For almost 200 years, the best rowers from schools, universities and clubs across the world have descended on this leafy town, around 40 miles west of London, to compete on the water. Over six days, 772 entrants from 27 nations will compete in 409 races over the mile-long course, watched by more than 300,000 spectators.

It is one of the highlights of the British summer social scene, part of a glittering quartet featuring horse racing at Royal Ascot, tennis at Wimbledon and Test cricket at Lord’s. All demand high standards of their ‘patrons’, and have ticket prices to match.

Henley has high sporting standards, and attracts current and future Olympians and top-level amateurs — but beneath the water, things are murkier.

Tests conducted last month around Henley, including on stretches of water used for the Regatta, by the environmental campaign group River Action discovered high levels of the potentially harmful bacteria E. coli in the water. From 27 tests, 1,213 E. coli colony-forming units (CFU) per 100ml of water were found. The United Kingdom’s Environment Agency considers that inland water registering 900 CFU or greater is poor. Ingesting water with those levels of E. coli risks possible serious illness.

As a result, rowing at the Regatta this year has come with a health warning. Rowers have been reminded of the importance of covering cuts, grazes, and blisters with waterproof dressings, taking care not to swallow river water, wearing suitable footwear when launching or recovering a boat, and cleaning all equipment thoroughly.

For the rowers, it has clouded what should have been one of the year’s landmark events.

“It concerns all the rowers,” says Sam Szeto, a 22-year-old cox of the women’s eight with the University of Bristol Boat Club. “I was ill in the weeks leading up to Henley Women’s in my first year because I got a lot of water in my mouth.

“We row on the River Avon (in south-west England) and the water is horrible there as well. It is full of sewage, especially when it has rained a lot. It’s a horrible oily film layer on the top of the water and you have to make sure everyone washes their hands, changes and showers straight after every session.

“Traditions like going swimming in the river after you get knocked out or throwing your cox in the river when you win can’t happen anymore — those are important traditions of Henley no longer happening. It’s quite sad to see.”

Jack Cushway, a 20-year-old rower with Oxford Brookes University Boat Club, is more matter-of-fact. For him, dirty water has simply become an occupational hazard.

“​​I would like to jump in the water after a session but I’m definitely not going to do that nowadays,” he says. “Where I’m from — the River Lea (which flows from Bedfordshire, through Hertfordshire and into north London) — the water is terrible. The situation with E. coli bothers me because you want the water to be clean.

“You won’t see many people jumping in after they win their races but you just have to get on with it. It might get us, it’s just down to luck.”

Henley is one of the biggest events on the British social calendar (Benjamin Cremel/AFP via Getty Images)

Henley is not the first meeting to be affected by poor water quality, and neither is it a problem entirely unique to the UK: rowers in regattas in the U.S and Canada have reported issues, while open water swimmers have been hearing warnings of dirty water in Paris’ River Seine before the Olympics, which begins this month.

In England, however, dirty water has become a staple of news bulletins in every corner of the country — and a significant campaigning issue in the General Election. In August, 57 swimmers fell ill after competing in the World Triathlon Championships in Sunderland, with some blaming the state of the water — a claim disputed by Northumbrian Water.

In March, rowers in the Oxford and Cambridge University Boat Race, another blue riband event in Britain’s sporting calendar, were strongly advised not to enter the water due to the risk of falling ill. Leonard Jenkins, the captain of the Oxford boat, revealed he had become unwell on the morning of the race and that several of his team had been affected by E. coli in the build-up. “It would be a lot nicer if there wasn’t as much poo in the water,” he told the BBC.

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Back at Henley, Marilou Duvernay-Tardif, 25, a rower with the Canadian national team, says there is increased awareness of the risks posed by dirty water compared to previous years.

“I heard a lot about it,” she says. “It was definitely on my mind coming here. I have very sensitive skin and I’m reacting to stuff like that. We’ve been just washing our hands right after rowing, not eating and being careful with water bottles — making sure there’s no water getting into them. I wasn’t super aware of it last year. There’s definitely a change.

“The lake we train on in Canada gives me a lot of skin problems. It’s something we’re talking about with the Federation in Canada to find a solution.”

Competitors have to take extra precautions this year at Henley (Benjamin Cremel/AFP via Getty Images)

There is, perhaps inevitably, a dispute around who should assume responsibility for the adverse findings.

River Action is blaming Thames Water, the company responsible for maintaining the water, for emptying raw sewage into the river, and is calling for tertiary treatment of sewage further upstream from Henley to ensure the regatta is safe again.

“That athletes are having the love of their sport threatened by this is outrageous,” said James Wallace, River Action CEO. “The fact it’s become normalised is unacceptable and very worrying.”

Henley Royal Regatta is supporting River Action’s findings, saying in a statement that “findings from the testing show that action must be taken now to preserve the blue spaces on which our sport relies”.

Thames Water, however, disputes the accusations. “We have been conducting testing for E. coli and intestinal enterococci in the River Thames in Henley since mid-May,” it said in a statement. “E. coli levels in the Henley stretch of the Thames are consistently achieving levels the Environment Agency would deem as ‘Good’ for bathing waters, during dry conditions.

“Our Sewage Treatment Works in the area have not released untreated effluent since May 14, demonstrating that multiple sources are likely to have contributed to these elevated readings.”

The cause of the high E.coli levels at Henley has been disputed (Benjamin Cremel/AFP via Getty Images)

Whatever the cause, rowing has suffered, whether that be the shredding of beloved Henley traditions and the damage to its prestige as a result or, more significantly, rowers not being able to trust the water they are racing on. With sports struggling to sustain participation levels, it is a controversy rowing could well do without.

Imogen Grant, a rower and qualified doctor who competed for Team GB in the lightweight women’s double sculls at the Tokyo Olympics in 2021 and will do so again in Paris, says it is “the apprehension of something you can’t control” that is most troubling for competitors.

“If it’s really bad that it causes you to be hospitalised it can completely disrupt your entire season,” she said. “It takes away from the enjoyment of the athletes as well. Around the Boat Race this year there was concern that some of the athletes might have been ill as a result of the water and that could have changed the results of the racing.

“It also sours the moment if you’re celebrating and it pops into your mind: ‘Wait a minute, I might get ill from this’.”

(Top photo: Andrew Matthews/PA Images via Getty Images)