Today at the Olympics: Keri-Anne Payne ready to suffer in the Serpentine in quest for gold

Britain's world open-water swimming champion faces test of stamina today

Keri-Anne Payne likes a challenge. For one she has her wedding to organise next month in Aberdeen. An autumn wedding in the north of Scotland – she will marry fellow Olympic swimmer David Carry – is an event able to defy even the best prepared; being an open-water swimmer might be just what is required.

Payne is the best women's open-water swimmer in the world and will dive into the Serpentine at lunch-time as favourite to win gold, but it is an event that is on a par with Scottish weather for its sheer unpredictability. There will be 25 swimmers in the field, including all the top-10 finishers from last year's world championship in Shanghai.

Payne was first over the line in Shanghai, to claim her second world title, but the entire top 10 finished within 20 seconds of each other – that after 10km. Compare that to the men's 1, 500m freestyle in the pool, where 20 seconds only covered half the eight-strong field finishing, and it offers an indication of the competitiveness of the women's event.

"I don't think Michael Phelps ever thought Ryan Lochte would ever beat him, but he has," said Payne. "That's the beauty of the Olympics – it's all about who is the best swimmer on that day."

It has been a long wait for Payne to get into the water. She had her final practice swim in the Serpentine – which has been praised by the competitors for the cleanliness of its water – yesterday under the guidance of Mark Perry, Britain's open-water coach. "She's in good form and she's ready to go," said Perry.

It is a race she has been preparing for since last July when she won the world title and in so doing became the first of Britain's 541 athletes to qualify for the London Games. It has been an exhaustive process, 10 two-hour sessions a week and one of five hours for a race that will leave her aching from head to toe – most swimmers finish with thumping headaches after two hours in the water.

"I am always pushing my body to the brink of potential illness because you have to push it as far as we can so it breaks down and rebuilds itself better," said Payne. "That's how the training works, so you are always at risk of pushing it too far. We're conscious swimming outdoors for too long could push you over the edge. You learn that as you get more experienced – when to take time out and how far to push it."

Four years ago she competed in the pool as well, but this time she has had to watch as her team-mates have struggled, with the honourable exception of Michael Jamieson and Rebecca Adlington, who will be a bridesmaid at Payne's wedding, and look on as elsewhere Britain's medal favourites have, largely, matched expectation.

She shared a room with Adlington in Shanghai, doing sudoku to pass the time, but this time it has been a more challenging wait. Britain failed to win a gold in 32 events in the pool – a silver and two bronze means the swimmers will fall short of their medal target of five to seven but a gold from Payne would offer a welcome dose of painkilling.

Four years ago Payne won silver behind Larisa Ilchenko. The Russian is not in London and the main challenge will come from the likes of Martina Grimaldi, a Neapolitan policewomen who took silver in Shanghai, the Australian psychology student Melissa Gorman, and Marianna Lymperta of Greece, the world bronze medallist. But any of the top 10 is capable of having a decisive day, or a disastrous one.

"Being an open-water swimmer you have to be versatile, being prepared for anything," said Payne. "We've always been taught as swimmers to expect the unexpected."

What's on TV...

BBC 1 9am-11.30am, 11.30-1pm, 1.45pm-4pm, 4pm-6pm, 7pm-10pm

BBC 2 1pm-2.15pm, 6pm-7pm, 10pm-10.40pm

BBC 3 8.55am-12.45pm, 12.45pm-7pm, 7pm-11pm

9.30am Canoe sprint finals Men's C2 1,000m begins, with the men's K4 1,000m at 9.48am. At 10.08am there's the women's K1 500m in Final A, featuring Britain's Rachel Cawthorn, before pair Abigail Edmonds and Louisa Sawers are in the women's K2 500m Final B at 10.42am.

10.00am Diving The semi-finals of the women's 10m platform event takes place.

11.30am Swimming The 10km women's marathon takes place and home hopes lie with Keri-Anne Payne. The 24-year-old – the first Briton to qualify for the Games – will be desperate to go one better after winning silver in Beijing.

From 12:30pm Dressage Laura Bechtolsheimer competes in the individual dressage Grand Prix freestyle, as do fellow Britons Charlotte Dujardin and Carl Hester.

1.00pm Football The bronze women's match bet-ween France and Canada kicks off at the City of Coventry Stadium.

1.45pm Sailing Watch action from Weymouth as the men's 470 sailing medal reaches its climax.

3pm Cycling The men's quarter-final of the BMX Track, featuring Liam Phillips.

4pm Boxing Nicola Adams, the two-time World Championship silver medallist, goes for gold in the flyweight final where she faces Cancan Ren of China at 4.30pm. Ireland's Katie Taylor is in the lightweight final at 4.45pm, in which she is up against Russian No 2 seed, Sofya Ochigava, a repeat of the world championships final.

5.00pm Basketball The opening semi-final in the women's event between Australia and United States.

7.20pm Athletics British hopes in the triple jump final had fallen on Phillips Idowu, but the 33-year-old failed to qualify in the top 12 on Tuesday.

7.30pm Athletics Great Britain's Lynsey Sharp goes in the women's 800m semi-finals.

7.45pm Football The women's final at Wembley between defending champions the US and Japan.

8pm Hockey Men's semi-final. Great Britain continue their quest to emulate the boys of '88 as they take on the Netherlands at the Riverbank Arena.

8pm Athletics Briton Andrew Osagie competes in the 800m men's final.

8.55pm Athletics In the men's 200m final, the spotlight falls on Usain Bolt to complete a second successive 100m and 200m double at an Olympic Games, having easily defended his 100m final title on Sunday. But the 25-year-old Jamaican faces stiff opposition from compatriot Yohan Blake, the second fastest man ever over the distance.

9.00pm Athletics Women's javelin throw final.

9.20pm Athletics The final event of the decathlon, the 1,500m, begins.

9.20pm Taekwondo Jade Jones competes in finals of the women's -57kg division at 10.15pm, while Martin Stamper lines up in the men's -68kg at 10.30pm.