Frankie Dettori called his mount Stradivarius "a tiger" after repelling the challenge of Southern France to win a second Yorkshire Cup.
The 4-5 favourite, trained by John Gosden, is only the second horse to win consecutive runnings of the one mile, six furlong contest which Ardross took in 1981 and 1982 under Lester Piggott.
Stradivarius' victory last year started a run that sealed a £1m bonus after the horse went on to win the Gold Cup at Ascot, the Goodwood Cup and the Lonsdale Cup.
The five-year-old will be aimed at the bonus again and is rated 6-4 favourite to land the Gold Cup again next month.
Ryan Moore, on Southern France for trainer Aidan O'Brien, tried to steal a march on his rivals and went clear but Stradivarius battled past, with Mildenberger in third.
"He's a tiger," said Dettori. "Once we got into a fight, I said: 'You do this.' Some horses are followers, he's a leader. It's a jockey's dream to have a horse like this."
Earlier, the William Haggas-trained Magnetic Charm carried the colours of the Queen to a narrow victory in the fillies stakes and could run next in the Coronation Stakes at Royal Ascot.
"The Queen doesn't go racing very often, so the more runners she can have while she's there (Ascot) and to run horses there with a chance is great," said the trainer's wife and assistant Maureen Haggas.
BBC racing correspondent Cornelius Lysaght
After Stradivarius won the first-ever long-distance race bonus so readily, organisers of the initiative maybe did well to find an insurer to support it again this time, however the premium may now go through the roof as, on the evidence of this, there's every chance of a repeat.
Despite the race being the horse's first since the autumn, that he had to concede weight and that he seems to thrive at further than this mile and three-quarter distance he won well even if reasonably narrowly.
When Dettori drew his whip in the straight things looked ominous for a stride, but he's probably a little lazy and was always holding the second.