Double Olympic champion James Cracknell is set to become the oldest person to compete in the Varsity boat race, with his Cambridge crew ranked as firm favourites to win the event on Sunday.

The 46-year-old retired from competitive rowing in 2006 but qualified for the event because he is studying a Master of Philosophy degree in human evolution at the University.

Cracknell, who won Olympic gold at Sydney in 2000 and Athens in 2004, would also become the most decorated man to row in the annual contest between Cambridge and Oxford.

British bookmaker William Hill said Cracknell’s inclusion has steered Cambridge from 11/10 outsiders to firm favourites at 1/5. Oxford are 7/2 to win the race.

“We aren’t sure whether it is the presence of James Cracknell in the Cambridge boat that has persuaded punters to part with their cash or the fact that people think they are much better,” said William Hill spokesman Joe Crilly.

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“Regardless of the reason, 62 percent of all bets and 95 percent of all the money placed on the race has been for Cambridge.”

Cambridge won all four races against Oxford last year, triumphing in the men’s, women’s and both reserve crew races at the event held on River Thames.

Cracknell battled through a rib injury, but insists being picked in the blue boat was among the proudest moments of his career.

"The sport has moved on in the way people row, and so you are having to learn to row the same way they do. There's no point in doing it your way," Cracknell told the BBC.

"There were times in this past six months when I was cycling for a bit when I had damaged a rib, and I was watching them all go, and I was wondering, 'what am I doing this for?'

James Cracknell will become the oldest entrant in the boat race (Getty)

"When I was told I was being put in the blue boat, I can honestly say it was as proud a sporting moment as when [British head coach] Jurgen Grobler sat me down and said 'you're going to be in the coxless four', because Steve and Matthew were trusting their sporting reputations with me.

"That was a prouder moment than winning at the Olympics, having their trust.