Frankel produced perhaps his finest performance on Saturday at Ascot to retain his unbeaten record with his 14th victory in the Group One Champion Stakes in what was his final race.
The Henry Cecil-trained colt - winning his 10th Group One race - had stumbled out of the barrier but recovered his poise to power home to beat last year's winner Cirrus des Aigles by 1 3/4 lengths.
"There has never been a better horse," said Cecil.
"I love everything about him. He's the best horse I have ever had. I'd be very surprised if there will be anything better."
The BBC then reported that Frankel's owner Prince Khalid Abdullah had confirmed the horse would be retired.
Winning jockey Tom Queally praised Frankel.
"No doubt he is better on better ground but his class showed today. I walked the track and was worried about conditions, but after walking the home straight I knew it was not too heavy for him to quicken up and go about his business and win," he said.
"In that respect, there was always a little worry but he was in great heart and looked a lot better than 12 months ago.
"What can I say about him? You never see an F1 car win on anything but tarmac but he may argue that case a little "
- Tom Queally, jockey
"What can I say about him? You never see a F1 car win on anything but tarmac but he may argue that case a little."
Frankel had looked out of sorts early on with his pacemaker, and older brother Bullet Train, and his jockey Ian Mongan, searching for him.
However, once Mongan spotted him he raced Bullet Train upsides Cirrus des Aigles while another of the main dangers Nathaniel sat in third.
Queally brought Frankel close to the fray on entering the straight, bringing an unprecedented roar to the crowd as the bell rang.
Cirrus des Aigles set sail for home but Queally, having dispensed with Nathaniel, came upsides the gallant French six-year-old and went past him with ease to justify his odds of 2/11 odds on favourite.
Although Olivier Peslier was able to conjure up a second burst from Cirrus des Aigles, Frankel was not to be denied and he strode out under the whip of Queally to breach the line, clear of his nearest pursuer who finished at odds of 9/2.
Nathaniel - who was beaten into second by Frankel on his first start in 2010 - stuck to his task to finish third at 9/1.
Queally, not normally one for expressing his emotions, returned to the winner's enclosure, punching his fist in the air as the crowd, who had roared him on as he turned into the final straight, stood and gave him a rousing reception.
The crowd also gave three cheers for popular trainer Cecil, who has been battling throat cancer over the past year.
Frankel didn't want to leave the scene as he went round the ring twice to ever greater acclaim before he departs for stud duties.
Frankel, who along with Cecil had also been applauded into the saddling enclosure prior to the race, had been a doubt earlier on Saturday because of the heavy going, but was passed to run after his connections walked the course.