Cruise liners, steam boats, jelly fish and the world channel record beware. Cassandra Patten, the Olympic swimmer who urged Queen Elizabeth II to make her Britain teammate and double gold medal winner Rebecca Adlington "a Dame by Christmas" and then won bronze in the inaugural 10k marathon swim in Beijing, is to take on a new challenge: she is training to race across the channel - and faster than anyone else at that.

Weather-permitting, Patten has what it takes to swim the 20.3 miles (swimmers usually cover at least five extra miles because of tides and currents) in a world-class time. The world record is held by Bulgarian Petar Stoychev in 6 hours 57.50mins, while Yvetta Hlavacova of the Czech Republic is the fastest woman, in 7 hours and 25mins.

Patten has invited comedian David Walliams, of the Little Britain television show, to give her tips for the crossing she is planning for August or September next summer after the open water world championships in Rome. The comedian crossed the channel in an astonishingly quick time of 10 hours and 34 minutes in 2006. "I would love to speak to David Walliams about his experience of swimming The Channel. I thought his performance was just breath-taking and a real inspiration for me."

Asked about the prospect of being kicked and punched by rivals in the Olympic marathon in Beijing, Patten replied: "I normally give them the three strikes rule. The first strike's an accident, the second strike 'you're playing on a dodgy line there', and the third time I give 'em one back... I'm a big girl so I can look after myself." That prompted teammate David Davies, who went on to win silver in the men's marathon, to say: "You know it's intentional when the girls take their handbags to the starting line."

Patten's crossing aims to raise £1m for charity. Patten, who covers the channel distance every two to three days in training, says: "I just need to get as many people as possible behind it and get the word out about what I am trying to do. It’s something I’ve always wanted to do since I was a little girl," says Patten. "There have always been two things that I have wanted to achieve - one is running a marathon and the other is swimming The Channel. Now seemed like the right time to give the Channel a go."

Patten’s coach in Stockport, Sean Kelly, agrees and thinks the break from routine will be as good as a rest fort the hard-working swimmer. "After the Olympics I think Cassie needed a new challenge and it’s nice for her to have a new target and set some different goals. This is a completely different mental and physical challenge to anything she has ever done before but I think that’s a good thing for her."

World records in the channel are as predictable as the weather: everything is possible. Patten and Kelly both talk in terms of strong possibility but the coach notes: "The conditions on the day will play a massive part. There is only so much she can do; she will be in hands of the weather and the tides."

Most who walk down to the shore worry about the cold, the jelly fish, fatigue. Patten fears loneliness. "The biggest difficulty I think I will have is swimming completely on my own. In open water races there are normally a lot of people around me and if the whole field swims slowly, in a tactical race, then I can still win. With The Channel it is just going to be me, on my own, against the clock. While there will be a support crew with me there will be very little interaction, so will be on my own for six or seven hours which I will find mentally quite tough. It will just be a race against myself."

Patten’s choice of charities are Children in Need, Mind, the mental health charity of which  Patten is a patron, and Right To Play, an athlete-driven international humanitarian organisation that uses sport and play as a tool for development of children and youth in the most disadvantaged regions of the world.