Gold Cup-winning rider Sam Thomas was hit with a 17-day ban after taking the wrong course on red-hot favourite Oumeyade at Fakenham.
The Paul Nicholls-trained 2-5 chance was in the lead going in front of the stands in the Light Dragoons Handicap Chase, but Thomas chartered a path on to the hurdles course by mistake.
He immediately realised his error and looked to the skies as he pulled his mount up.
The race eventually went to 11-1 chance Tipp Top, who just got home by a length from Log On Intersky.
The stewards not surprisingly handed out a hefty punishment to Thomas, whose finest hour came at Cheltenham in March when he partnered Denman to a brilliant success in the Cheltenham Gold Cup.
He will be out of action for 17 days, having been given 14 days for taking the wrong course and three days for careless riding.
Thomas will be stood down from June 1 to 20 on days when jumps racing takes place.
Speaking from his Ditcheat base, Nicholls said: "I didn't go to Fakenham, but I saw what happened.
"We all make mistakes so we've just got to take it on the chin and live with it.
"It's just one of those things that happens."
The young rider gained some measure of compensation when steering 5-2 chance Roby De Cimbre to success for Nicholls in the Michael Dellow Beginners' Chase on his final ride of the day.
Thomas is not the first jockey to be caught out at the Norfolk track. In January, Denis O'Regan was in trouble when he rode a finish too soon, with the stewards handing out a 14-day riding ban.