Thornton came off so often - seven times consecutively during one dark period - that he was advised to seek alternative employment. Kim Bailey, the trainer Thornton joined after riding successfully in the north for Arthur Stephenson, more or less fired him.
Thornton's girlfriend, Jill Richardson, shared as much in the anguish of a career that was going nowhere as she did in the joy of his Gold Cup victory yesterday on the 25-1 shot Cool Dawn. A resolute redhead, who spoke while receiving calls of congratulation on her mobile telephone, she set out the hard times to put Thornton's achievement into proper perspective.
"Watching Andrew ride a couple of years ago it wasn't a case of would he fall but when. Soon he had no confidence at all. It was sad because he was riding horses that had no chance of winning or show his ability." Probably, the thought in Thornton's mind then was that he had made a wrong career move.
A rugby footballer of such promise at Barnard Castle, the public school that turned out Rob Andrew and the Underwood brothers, Thornton had the potential to follow them into England's colours. Instead, he chose the rough and tumble of an even harder game and the pain that goes with it.
The painful period with Bailey was a test of his resolution. In once season alone Thornton suffered seven fractures of the collar bone. "He just wouldn't give up," his girlfriend said. "Kim Bailey made it pretty clear that he didn't think Andrew had much of a future but he asked to stay on in the yard." Things took an upward turn for Thornton when he rode a double in Scotland. There was a technical change, too.
The tallest jockey in the weighing room at Cheltenham yesterday, Thornton was advised to lengthen his stirrups. In reply to one of the many calls she received in the unsaddling closure, Jill Richardson said: "Yes, the advice paid off."
Riding longer made such a difference to Thornton's balance that his career was transformed. He struck back with 26 winners and won the King George VI Chase at Kempton last Boxing Day on See More Business for Paul Nicholls.
On Wednesday came Thornton's second Festival winner when he brought French Holly home in the Royal and SunAlliance Chase. At a party to celebrate French Holly's victory Thornton passed on the champagne. "You carry on," he said to friends, "but I've got a big day tomorrow."
Going off at a price long enough to show that not a great deal was expected of it, Cool Dawn would make a mess of general predictions. When they went down to the start on a day of warm sunshine most eyes were on Dorans Pride who was well backed to bring Ireland another victory.
As emphasised by a flood of money for Florida Pearl on Wednesday, short prices don't deter the Irish if they can smell a winner and there was plenty riding on Dorans Pride when the field set out in the Gold Cup. The sight of Indian Tracker and See More Business being taken out of the race by the suddenly lame Cyborgo strengthened confidence in Dorans Pride but a mistake three out did for Ireland's principle challenge.
No Irish celebrations this time, no repeat of the wild excitement that greeted Charlie Swan when he returned to the unsaddling enclosure with Istabraq on Tuesday.
It made no difference to Thornton. Yet he had stayed in the game, ridden out the bad days and nobody could take this one away from him.