Workforce, the leading European 3&#45;year&#45;old, faces older horses for the first time in his brief career Saturday at Ascot in the $1.5 million King George VI and Queen Elizabeth Stakes in which he will be sorely tested by his Michael Stoute&#45;trained stablemate and recent course&#45;and&#45;distance winner Harbinger.Highly impressive when winning the Epsom Derby by seven lengths on June 5, Workforce was held out of the Irish Derby by Stoute and owner Khalid Abdullah expressly for this 1 1/2&#45;mile Group 1 race, which will be just the fourth start of his career. But while the son of King&rsquo;s Best looked terrific at Epsom, the form of the Derby has not worked out particularly well. Runner&#45;up At First Sight has been unplaced twice since then, while fourth&#45;place Jan Vermeer has been third in both the Irish Derby and the Grand Prix de Paris. Eighth&#45;place Buzzword has won the German Derby, but that is hardly a high&#45;profile advertisement for a race like the King George.Although Ryan Moore has chosen Workforce over Harbinger, Workforce&rsquo;s lack of experience may do him in, making Harbinger the choice with big&#45;race specialist Olivier Peslier flying in from France for the ride.Harbinger may be the most improved horse in the world this year. The Dansili 4&#45;year&#45;old is 3 for 3 this season, with victories in the 1 1/2&#45;mile, Group 3 John Porter Stakes and the 1 5/8&#45;mile, Group 3 Ormonde Stakes. Last time, he cruised to a 3 1/2&#45;length score in the 1 1/2&#45;mile, Group 2 Hardwicke Stakes in a performance that was rated higher by the Racing Post than the Group 1 Royal Ascot victories of Goldikova, Starspangledbanner, and Byword.Three&#45;year&#45;olds have won 27 of the King George&rsquo;s 59 runnings, but 4&#45;year&#45;olds have won the last six renewals, with two of those winners, Dylan Thomas and Duke of Marmalade, trained by Aidan O&rsquo;Brien. O&rsquo;Brien&rsquo;s 4&#45;year&#45;old Fame and Glory is the highest&#45;rated older horse in Europe, but he stays at home Saturday to await the Irish Champion Stakes on Sept. 4. In his place, O&rsquo;Brien will saddle Irish Derby winner Cape Blanco. The Galileo colt beat a very inexperienced Workforce into second in the Dante Stakes on May 13 but was only 10th in Lope de Vega&rsquo;s French Derby. Suited by 12 furlongs, he will be without the services of the suspended Johnny Murtagh, who is replaced by Colm O&rsquo;Donoghue.Three&#45;time Arc runner&#45;up Youmzain was unlucky last time when a nose second in the Grand Prix de Saint&#45;Cloud. He should get his preferred fast pace Saturday as Stoute also will saddle a rabbit in Confront. Two very dangerous distaffers, Dubai Sheema Classic winner Dar Re Mi and French raider Daryakana, winner of the Hong Kong Vase and just a short neck behind Youmzain when third in the Grand Prix de Saint&#45;Cloud, make this the deepest King George since Alamshar beat Sulamani, Kris Kin, and Falbrav in 2003.