Calandagan landed the big race on British Champions Day, Powerful Glory made history with a 200-1 triumph and Cicero's Gift was another shock winner at 100-1.
French challenger Calandagan, ridden by Mickael Barzalona for trainer Francis-Henri Graffard, won the Champion Stakes from Ombudsman at Ascot.
Powerful Glory, ridden by Jamie Spencer for trainer Richard Fahey, beat 2-1 favourite Lazzat into second in the Champions Sprint Stakes.
Powerful Glory is the longest-priced winner of a top-level British Group One race, three months after Qirat set a record by winning the Sussex Stakes at Goodwood at 150-1.
Spencer came with a late surge on his mount to triumph on Britain's richest race day, with 66-1 shot Quinault third in the 19-runner contest.
"I am lost for words," said Spencer.
"Powerful Glory is a good horse and travelled nicely. I thought I was going to be placed and all of a sudden I thought I actually have a chance."
There was another big upset with 100-1 chance Cicero's Gift winning the Queen Elizabeth II Stakes under Jason Watson for trainer Charlie Hills.
A tearful Watson came home ahead of The Lion In Winter and Alakazi to claim his first Group One win since 2019.
Much of the talk in the build-up to the Champion Stakes was around Ombudsman and Delacroix - meeting for the third time, with the score one apiece - and their trainers.
Delacroix's trainer Aidan O'Brien had suggested John Gosden, who trains alongside son Thady, liked to "whinge" sometimes after races.
Gosden, who had alluded to O'Brien fielding multiple runners in some big races, said his comments had "irked" his Irish counterpart.
But they were both out of luck as 15-8 shot Calandagan, runner-up last year, prevailed by two and a quarter lengths from Ombudsman, with Almaqam third and Delacroix fourth.
It was another big victory in the Aga Khan's colours for Graffard and Barzalona, who won the Prix de l'Arc de Triimphe with Daryz two weeks ago.
"He's a very good horse. It's a joy to ride in these colours and I'm very proud to be part of the team," said Barzalona.
Powerful Glory had been well beaten in his two previous races this season, although had won on both starts last year, including the Group Two Mill Reef Stakes.
"I am not saying I thought he would come here and nearly win, but I knew he would do his best and, when I saw 200-1, I nearly had a bet and I don't bet," said Fahey.
"We have seen the real Powerful Glory today - and he has only had four starts."
Powerful Glory, owned by Sheikh Rashid Dalmook Al Maktoum, earned nearly £320,000 on a day which boasts overall prize money of £4.35m.
Earlier, Trawlerman beat stablemate Sweet William in a Long Distance Cup one-two for the Gosdens.
Kalpana, ridden by Colin Keane, defended her Fillies and Mares Stakes title for trainer Andrew Balding.
Meanwhile, Oisin Murphy was crowned champion jockey for a fifth time after a turbulent year.
Murphy was fined £70,000 and given a 20-month driving ban for drink-driving after crashing a car into a tree in April.
The jockey, who has well-documented alcohol issues, apologised for what happened.
"I certainly had a point to prove that I was able to do my job with things going on externally, and that's what motivated me and fuelled me to the championship title," he said.
"Like anyone with an addiction, you have to work very hard at it. And, unfortunately for me, I relapsed and I've had to pay the price for it since."