The extraordinary situation has come about because Andrew Thornton, the professional who took over from Harding when it became apparent the horse owned more talent than a part-timer could extract, has opted to ride Super Tactics, trainer Robert Alner's other runner in the race.
Harding, 30, has won two hunter chases on Cool Dawn, but has not ridden under Rules since finishing last of seven finishers on her 10-year-old over tomorrow's course nearly a year ago. At that point she and Alner agreed Thornton should take over and the horse won four times in open company, culminating in his Gold Cup triumph.
Harding said yesterday: "I was gobsmacked when Robert phoned me to ask if I wanted to ride. I am pretty fit as I have been out of work for four months so I have been riding more than I would have done otherwise."
Thornton, who will take over again on Cool Dawn after tomorrow, admitted the choice between the two horses was difficult, but his decision must be a tip in itself. He said tactfully: "It is very difficult to get off a Gold Cup winner but at the end of the day it comes down to my judgement and I wouldn't be the first jockey to choose wrong."
This scenario could happen only in the sometimes rather cosy jump racing world. Memo to footballers: if you want to get in the first team, buy the ball.