Jessica Ennis is already the face of London 2012 and gold medal glory could see her earnings go through the roof as companies clamour to sign her up.

But experts said the heptathlete, who already has a number of sponsorship deals in place, would have to be careful or she could end up with more endorsements than she can cope with.

Simon Chadwick, professor of sport business strategy and marketing at Coventry University Business School, said he expected the 26-year-old's earnings to double from around £1 million this year to £2 million the next.

He said: "She's had a pretty good year already this year. It looks like her earnings last year were somewhere in the region of £600-700,000. This year it's looking like £1 million already from her endorsement deals just in the run-up to the Olympics. She already has a strong catalogue of endorsements such as Jaguar, Powerade, British Airways, Aviva, Olay."

He said athletes typically have performance clauses in their contracts that dictate how much they are likely to earn.

"For example if an athlete qualifies for the Olympic Games, they will receive a particular payment, and if they get into the final they will get another one, and then if they get a gold medal, they will get an even bigger pay-out.

"In simple terms, the better she does the more she's paid. By winning gold she will boost the income from her existing contracts," he said.

"It will be interesting to see if she will be able to renegotiate her existing contracts. In terms of bringing in new sponsors, I think this could be a bit of an issue for her.

"She's already got, as far as I can see, seven endorsements and to sign more could be a strain on her. Once you get up to eight, nine, 10, that's a lot of commercial endorsement deals to fulfil.

"Plus as she is already signed to Olay, then they are unlikely to want her to become associated with other beauty products, and the same with British Airways and other travel companies."

But he added that no big supermarket trains are currently associated with Ennis so this could be a route for her to go down.

"She doesn't have a megabucks sports merchandise deal so there might be opportunities for that," he added. "Her advisers and management need to work very, very carefully now as commercially she is very, very valuable. If you're Jessica Ennis in January 2012 renegotiating a contract then that's a very different position to if you're Jessica Ennis renegotiating a contract tomorrow."

But he added that it was a "sad reality" that female athletes do not earn as much as men from sponsorship deals.

"If they want to earn huge amounts, they are going to have to do it on a global basis," he said. "I think for Ennis to earn the same amount as say, Andy Murray, she's going to have to get a much more global profile and typically female athletes just don't have that kind of international profile.

"In relation to male athletes she's not about to go stratospheric but in relation to domestic female athletes she is. She'll be rich, there's no doubt about it, but if she was a man she'd be richer."

He said tennis players Maria Sharapova and Anna Kournikova were the best examples of sportswomen who have managed to command a global audience and earn large amounts more comparable to men.

Prof Chadwick said Ennis's popularity to brands lies not just in her success and talent but in the fact the university-educated athlete is intelligent and good looking.

He added: "If you look at the likes of Tiger Woods, I think part of his success is in his mixed heritage, which makes him appeal to lots of consumer segments all at the same time. I think this is something that will also work in Ennis's favour."

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