In which race did Frankel achieve his highest Timeform rating?

On October 15, 2011, on the final start of his three-year-old campaign, Frankel ran on powerfully to beat Excelebration by 4 lengths in the Queen Elizabeth II Stakes, over the straight mile at Ascot, as a result of which he was awarded a Timeform rating of 143+. At that stage of his career, Frankel was rated just 2lb inferior to Sea-Bird, awarded a Timeform rating of 145 after winning the Prix de l’Arc de Triomphe by six lengths, although the ‘+’ attached to his rating indicated that he ‘may be be better than rated’. Indeed, Timeform hailed the ‘bold and refreshing decision’ by owner Khalid Abdulla to keep Frankel in training as a four-year-old.

So it proved, because on June 19, 2012, on the second start of his four-year-old campaign and his eleventh start in all, Frankel recorded an extremely impressive 11-length victory over his old rival Excelebration in the Queen Anne Stakes, over the same course and distance, to achieve a Timeform rating of 147+. Frankel did not better that rating when stepped up to a mile and a quarter, and beyond, in the Juddmonte International Stakes at York and the Qipco Champion Stakes at Ascot, but nonetheless remains the highest-rated horse in the history of Timeform.