It had been assumed that the Irishman, who landed the Gold Cup on Master Oats in 1995, would partner Teeton Mill and ride Edward O'Grady's Nick Dundee in the Royal & SunAlliance Novices' Chase the previous day.
However, speculation that Nick Dundee will instead take his place in the Gold Cup has caused a dilemma for the jockey. With an announcement on Nick Dundee's chosen race expected at the weekend, Stephen Winstanley, boss of Teeton Mill's owners, The Winning Line, claimed yesterday that Williamson had agreed to ride the Venetia Williams-trained grey, on whom he has won the Hennessy Gold Cup and King George VI Chase.
"All I can tell you is that Venetia has assured us that Norman Williamson will ride the horse," he said. "We will be disappointed if he doesn't and, quite frankly, amazed.
"I am not happy about the situation as it stands and we have made contingency plans if he doesn't ride. We won't be left without a top jockey for the race, that I can assure you."
Williamson, regular partner of both horses, stressed he has not ruled out riding Nick Dundee, who runs in the colours of Sue Magnier, should the gelding run in the Gold Cup.
"I am pretty sick of it all," he said. "I met Mr Magnier yesterday and we spoke at length. I appreciate that people want me to make a decision but there is no point in me saying what I ride until a decision about Nick Dundee is made."
Dato Star is a surprise withdrawal for the Champion Hurdle, for which 17 entries were confirmed yesterday. The eight-year-old is "not moving properly" according to his trainer, Malcolm Jefferson.
Last year's record-equalling 12-length winner Istabraq, his stable-companion Theatreworld, runner-up for the last two years, and Bellator (who unseated his rider at the last) are the only other acceptors to run in the race 12 months ago.
Bellator is the only representative of Venetia Williams, who has withdrawn Happy Change and Stretarez. Others taken out were Juyush, Prince Of My Heart, Toto Toscato and last year's fourth, Pridwell.
n Lord Gyllene has been ruled out of the Grand National. The 1997 winner has suffered a pelvic stress fracture and will miss the rest of the season.
n Francois Doumen has decided against sending any runners to Cheltenham next week, including his highly regarded Newbury winner Quel Senor.Reuse content