Runaway Irish Derby winner Montjeu put up probably the best performance in the race for seven years, it was claimed officially yesterday.

Senior Irish handicapper Ciaran Kennelly has put a tentative rating of 128 on the French colt's five-length defeat of Epsom runner-up Daliapour, who was in turn five and half lengths clear of third-placed Tchaikovsky.

That would make it the best effort in the Curragh Classic since St Jovite scored by 12 lengths from Dr Devious in 1992.

"I haven't had a chance to discuss it with the French handicapper and I would like to check it with him but I would have thought Montjeu would be rated in the region of around 128," Kennelly said.

"He beat Daliapour by five lengths and Oath beat him by two lengths at Epsom. That makes him three lengths better than Oath; three lengths over a mile and a half is generally worth 5lb and Oath is rated 123 in England."

Montjeu is now likely to be aimed at the Prix de l'Arc de Triomphe and Kennelly stressed that the colt's rating is subject to reassessment.

Meanwhile, Frankie Dettori will decide today whether to fight the lengthy ban he was handed at the Curragh on Sunday. The Italian, riding at Maisons-Laffitte yesterday, was seething after he was stood down for a total of 12 days, and he has been in touch with Jockeys' Association secretary Michael Caulfield.

But Caulfield revealed that no decision on an appeal will be made until this morning. Dettori was banned for improper riding on Altibr and for using a defective back protector, which had no crotch strap so as to avoid aggravating a previous haemorrhoid condition.

The suspension rules him out of the last two days of Newmarket's July meeting, York's John Smith's Cup fixture and the Weatherbys Super Sprint card at Newbury.