Camborne (7/1) displayed a decisive turn of foot to defy top-weight and record an emphatic success in the Ladbrokes Mallard Handicap.
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Rab Havlin bided his time on the John Gosden-trained five-year-old until unleashing him with a potent challenge.
Shwaiman, who was receiving 26lb, had no answer to that burst of acceleration and had to settle for second place, two lengths away.
"They didn't go much of a pace so thankfully he didn't have to go flat out under top weight for too long," said Havlin.
"He's always shown a good turn of foot in his races and he's shown before he can come from the back in big fields. You can only ride him that one way and I just had to wait."
The winner was cut from 20/1 to 16/1 for the Cesarewitch by Sky Bet.
James Fanshawe, trainer of runner-up Shwaiman, said: "He loves this ground and hopefully he will run again this year. We can go two miles and he's a nice staying prospect for next season."