It will be a fairytale Grand National result if Tony McCoy supplies a perfect climax to jump racing’s most successful career at Aintree today.

But it will also be a slightly bittersweet one for McCoy.

A month shy of his 41st birthday, and a couple of weeks before being crowned Britain’s champion jockey for a 20th time, the Co Antrim-born rider has set a line in the sand by confirming that if the favourite, Shutthefrontdoor, wins, he will retire on the spot.

For someone whose timing in the saddle is famously precise, it’s a no-brainer – the sport’s most famous jockey signing off in the sport’s most famous race, a race he spent a decade and a half desperately trying to win until memorably succeeding in 2010 on Don’t Push It.

However, McCoy has spent his career confounding expectations and, despite already stretching the boundaries of endurance in a career where it is a matter of “when” rather than “if” you get hurt, he admits retirement holds no attraction.

Set to finish anyway at the end of the British season in a fortnight, his famous intensity has shown no signs of wavering since he announced his plans in February and if Shutthefrontdoor doesn’t win, McCoy is likely to relish a few more weeks doing what he loves.

“I have mixed emotions. I would love to win the National – but I don’t want it to be my final ride. I really don’t want to retire. But if I win, I’ll do retirement after that,” he said.

Don’t Push It’s victory transcended the sport to such an extent McCoy was voted BBC’s Sports Personality of the Year on the back of it, a reflection of the unprecedented impact success in racing’s toughest race by its toughest competitor had.

A win today would put even that in the shade in terms of public impact and, although McCoy’s two decades at the top have cured him of illusions about the toll riding over fences can take, the National does have a habit of throwing up fairytale outcomes.

Red Rum’s hat-trick in 1977 and Aldaniti’s emotional triumph in 1981 are among those contributing to a dramatic legacy that is unparalleled in the sport. It is a legacy that, in the long run, means no single figure can ever be bigger than the National itself.

But a win for McCoy in racing’s longest race could make it a close-run thing in the short term.