Mogul got his career back on track with a commanding victory in the Juddmonte Grand Prix de Paris at ParisLongchamp.
The son of Galileo began the year as one of Aidan O'Brien's leading Derby pretenders but could only finish sixth at Epsom, following defeat at Royal Ascot the previous month, and his St Leger hopes were seemingly quashed when he was only third in the Sky Bet Great Voltigeur at York last time.
However, the 6/1 victor was right back to his best in Paris, travelling sweetly on the inside near the back of the field in the hands of Pierre-Charles Boudot before quickening up smartly approaching the final furlong and going on to win by two and a half lengths.
Epsom hero Serpentine had looked the pick of the O'Brien team beforehand, but despite enjoying a perfect trip in fourth throughout, as stablemate Nobel Prize ensured the race was run at a good clip, he looked one-paced when the tempo increased and could only finish fourth.
In Swoop stayed on strongly in the closing stages to snatch second from fellow French runner Gold Trip, but English King proved a bitter disappointment again as he was well beaten.
O'Brien said of Mogul: "We’re delighted with him, we always felt he was only coming and I’ve been saying it a while.
"He showed so much speed that we felt maybe dropping to a mile and a quarter might be the right thing to do, so we said today to ride him for speed and take your time on him.
"He’s obviously a fast horse as he’s able to quicken.
"Mogul is in Australia (Cox Plate) and he could go to America, or if we do decide to step back he could go for the Champion Stakes or maybe Hong Kong. There’s a lot of options for him.
"Christophe was happy with Serpentine. I was thinking of the Arc and I’m encouraged with how happy Christophe was with him."