Daryl Jacob and Leighton Aspell have failed in their appeals against suspensions that will rule them out of the lucrative Christmas racing period.
Wexford-born Jacob, who enjoyed a career-high victory when the Paul Nicholls-trained Neptune Collonges prevailed by a nose in the Aintree Grand National in April, was handed a 10-day sentence after prematurely easing Ulis De Vassy at Wincanton last week.
The duo jumped the last flight of hurdles in front, but had just been passed by Quaddick Lake when Jacob, as he admitted in yesterday's hearing at the British Horseracing Authority in London, mistook a path for the winning line.
His defence centred on the theory that he would not have won the race anyway, but the appeals panel upheld the ban, stating that his mount, beaten a quarter of a length, "could have won".
The sanction will begin next Thursday, meaning Jacob will miss the ride on Kauto Stone for Nicholls in the King George VI Chase on St Stephen's Day, having won a Grade One on the horse at Down Royal last month.
Aspell, from Narragh More in Kildare, is struck off for two weeks from the previous day after he and Oliver Sherwood were found guilty of schooling Furrows in public at Hereford last week.
Their appeal was also dismissed, with the horse banned for 40 days and its Lambourn handler left facing a £3,000 fine.