Frankie Dettori has chosen to ride Arrest rather than Royal Ascot winner Gregory in Saturday’s Betfred St Leger at Doncaster – his final ride in a British Classic.

Dettori had looked sure to partner the John and Thady Gosden-trained Gregory given the way he won the Queen’s Vase in June over the St Leger trip – but Kieran Shoemark will now step into the breach.

Gregory only lost his unbeaten record last time out when dropping down to a mile and a half in the Great Voltigeur at York behind the re-opposing Continuous.

However, recent rain at Doncaster has turned the ground soft meaning Dettori will have a second chance at Classic glory on the Gosdens’ Arrest, who was sent off favourite for the Derby but could finish only tenth on good to firm ground.

He also disappointed on quick ground at Royal Ascot but was impressive back on a soft surface at Newbury against older horses in the Geoffrey Freer last time out.

The Clarehaven stable also has a fine third string in the supplemented Middle Earth (Oisin Murphy), a hugely impressive winner of the Melrose at York’s Ebor meeting.

The King and Queen have a real live chance of tasting success in a British Classic with the William Haggas-trained Desert Hero, himself a Royal Ascot winner, albeit in handicap company in the King George V Stakes.

He subsequently won the Gordon Stakes at Goodwood, narrowly beating Simon and Ed Crisford’s Chesspiece and the two will lock horns again.

Aidan O’Brien runs four, Great Voltigeur winner Continuous, Alexandroupolis, Denmark and Tower Of London meaning there were no withdrawals at the 48-hour stage.