Frankel enhanced his status as the world's top-ranked horse, winning the Queen Anne Stakes on the opening day of Royal Ascot by 11 lengths to improve to 11-0.
The 4-year-old colt, ridden by Tom Queally, beat 11 rivals in the 1-mile Group One race.
Expectations were high and his trainer, Henry Cecil, said he was relieved
Frankel had not disappointed his fans.
"There's no such thing as a certainty. He is a great horse ... He did exactly what I thought but he's still improving," Cecil said.
Rated the best horse for at least the past 25 years by the British Horseracing Authority last month, Frankel tracked pacemaker Bullet Train before taking the lead three furlongs from home.
The Aidan O'Brien-trained Excelebration finished second, marking his fifth defeat by Frankel, just ahead of Side Glance.
"We were delighted with our horse but Frankel is unbelievable," O'Brien said.
Last year, Frankel won the St. James's Palace Stakes on the opening day of the 300-year meet.
"It's just a demolition again. He was awesome," said Queally, who also rode Frankel to last year's Ascot victory.
He said the horse has improved since then.
"He settled, he travelled, he got everything else off the bridle when I was still sitting there. He's amazing," Queally said, adding that the race was Frankel's best performance so far.
"He ticked all the boxes, he did everything right. From my point of view he's been flawless in the past but I couldn't have asked for anything more."
Queen Elizabeth II, who is celebrating the Diamond Jubilee to mark her 60-year reign, arrived at the meeting with the royal family in their traditional carriage procession around the course.
The Queen has been to every Ascot meeting since 1945.
Frankel's outstanding performance has put additional pressure on the other undefeated sensation at Ascot, Black Caviar.
The five-year-old Australian mare is ranked No. 2, behind Frankel, and will aim to extend her record of 21 unbeaten starts when she races in the Diamond Jubilee Stakes.
Black Caviar recently broke a long-standing Australian record for consecutive wins, eclipsing the 19 victories of Desert Gold from 1915 to 1917 and of Gloaming from 1919 to 1921.
The 1,200-metre Group One race will be Black Caviar's first start outside Australia.
AP