Twenty-six years after a first win in the event's most prestigious race, Dettori claimed number six on Thursday as the four-year-old joint-favourite edged clear on the home straight.
The four-year-old was beaten a length into third place by Order Of St George in the Long Distance Cup at Ascot last October, but a winning return in last month's Yorkshire Cup suggested he could be an improved performer this season.
"Frankie keeps telling me it's his sixth but I told him not to forget the horse that got him there", said Gosden. He managed to get within a neck and once he couldn't get past me, I knew my horse was courageous and that was it.
"What a courageous horse!"
"It was thrilling to win a Gold Cup in that manner".
"The crowd got behind it". It was mental and I was loving it. To have the three best horses in the last furlong battling it out, you can't beat it. "The Gold Cup is the showcase of the week and to win it again, my first one for John Gosden, is great for the team".
A classic renewal of the race saw four horses lock horns on the home straight but it was the four-year-old who got the better of an epic battle to give the Italian jockey a remarkable 60th victor at the royal meeting. But as he clarified: "It is my sixth and my 60th - but I'm only 47, don't mix it up!"
■ 16 - Runners will line up for today's Hampton Court Stakes at Royal Ascot.
"It's lovely to win the Gold Cup", he said. But luckily he stuck his neck out and went on. It was a stunningly good race. "He is a dear horse and he is not very big", Gosden said. "He's a gorgeous little horse - I could see Wyatt Earp riding into town on him".
Stradivarius was found to be lame after a routine post-race examination having lost his right-hind shoe.
Victory for Gosden and Dettori was the ideal antidote to the crushing disappointment of their odds-on chance Cracksman getting beaten in Wednesday's feature race the Prince of Wales's Stakes. John Gosden's colt won the Queen's Vase at last year's Royal meeting and went on to lift the Goodwood Cup.
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