Rondetto has fallen, Princeful has fallen, Norther has fallen, Kirtle-Lad has fallen, The Fossa has fallen, there's a right pile-up. Leedsy has climbed over the fence and left his jockey there. And now, with all this mayhem, Foinavon has gone on off on his own . . . he's about 50, 100 yards in front of everything else. . .'

MICHAEL O'Hehir had a system. For two months before every Grand National, he sat down with pieces of paper on a cleared table and with a cleared mind he set about building a database.

Come April, there'd be three dozen horses setting out for the 30 Aintree fences but in late January and early February, there'd be maybe treble that number to input on the off chance they'd make it to Liverpool. He had to get his head around them all . . . the chanceless as well as the chances.

The system had a second phase. Come race-day, he'd sweet talk his way into the weighing room an hour before the race and as each jockey stood on the scales, he'd tick off the colours in his mind's eye. These were the days long before Attheraces and 48page colour supplements and so seeing shades of blue and tinges of red for himself turned what had been a collection of artist's impressions into a live feed. And sometimes, like on this day 40 years ago, he came across a hole in his research and moved to patch it up.

The black silks with red braces-style strips that hung around Johnny Buckingham's shoulders didn't compute.

O'Hehir flipped through both his pages and his memory and couldn't place them. So he pulled Buckingham aside and asked what he was riding.

Turned out that the horse had, up until a fortnight before, been owned by two men but one of them had tired of the drudgery involved and sold his share to the other. Mr Cyril Watkins . . . for it was he who now owned the horse outright . . . decided on a colour change.

When O'Hehir asked, Buckingham said that the colour change was for luck. A 100-1 shot with a jockey riding in his first National, an owner who didn't feel enthused enough to attend the race and a trainer, John Kempton, who chose to go to take a ride in Worcester instead of going to Aintree, luck was about all that Foinavon could have hoped to have going for him.

Buckingham didn't grow up with horses. He never sat on one until he was 15, having had neither inclination nor opportunity up to then. Even after he'd started, it took him an age to get comfortable. He rode his first race in 1957 but over the years that followed, being a jockey interested him more than it defined him. In time, it seeped into his blood and he became better-known, even managing a win at Cheltenham. But he was rarely on the tip of anyone's tongue when it came to booking rides.

He famously only got the Foinavon one by default.

Kempton would definitely have ridden him but he couldn't make the 10-stone weight.

With three days to go to the race, Buckingham's phone rang. There was barely time to make arrangements and after just about making it to Liverpool on the Friday, the best he could do so far as a bed went was a sofa in some digs across the road from the track.

So Foinavon arrived at Aintree with only his lad and his stable companion, a small goat named Susie, for company.

When Buckingham explained the black silks with the red strips to O'Hehir, he did so not dreaming that the commentator would have to call on the new knowledge.

That said, he still feels he should right some wrongs that have held down the ages. For one thing, the reason he was far enough behind not to be brought down when the pileup came wasn't that Foinavon was simply too useless to keep up. Okay, he was 100-1 shot, but Buckingham says he had deliberately settled him in off the pace. Right beside him as they jumped Becher's Brook, the fence before The Fence, was Josh Gifford on 15-2 favourite Honey End. Buckingham had always regarded Gifford as the best judge of pace around and had figured that in his first Grand National, he was as good a man to track as any. When the others went off at such a ferocious pace, Foinavon held back.

What happened next is as vital a piece of Grand National lore as Red Rum and Aldiniti and Devon Loch and all the rest. Popham Down, a loose horse, arrives at fence 23 and doesn't fancy it. He swerves to his right at the very last second, knocking Rutherfords sideways. The dominoes fall from there to their ghoulishlooking end with horses thrown through the fences, horses refusing, jockeys cast into the air like flies on a fishing line. In a trice, it was a steaming pile-up, bodies and horseflesh everywhere, the most remarkable image in Grand National history.

"It all happened so quickly.

The horses ran down the fence and all of a sudden, there were horses coming back towards me, horses upside down, jockeys lying everywhere. Then, literally a few yards from the fence, I had to turn him almost totally sideways to miss Josh on Honey End and he took the fence pretty much from a standstill. You have to give the horse so much credit."

The wonder is that anything jumped it at all. Quite apart from the fact that there was hardly any room, the sight of a large field of horses either lying prostrate or struggling to their feet or, in some cases, running back towards them should have spooked any horse still standing. It happened to Honey End who, having picked his way through, refused when he got to the fence. It happened to KirtleLad who, having been remounted by Paddy Broderick the far side of the fence, refused at the next. But it didn't happen to Foinavon who, with Kirtle-Lad's exit, was left with the freedom of Liverpool and only six fences between him and the finishing line.

"He was a lazy old bugger at the best of times, " says Buckingham, "so to have him away out on his own with more fences to jump was nervy, I can tell you. I was afraid all the way that he'd just take it into his head that he didn't need the hassle any more and would come to a stop. But he did it well. Credit to him, he did it well. Maybe jumping the last it looked like Honey End (Gifford had remounted) might catch us but once Foinavon saw the rail, he bucked himself up again and did it quite easily in the end."

Did it change his life? It did and it didn't. The good rides came dropping less slowly in the couple of seasons that followed but he never made it to the top of the game. Come 1971, the life was becoming a chore. If it wasn't for bad horses, he'd have had no horses at all. You wouldn't call what he was making a living and being around racing was really the only reason he kept at it. But when Richard Pitman overheard him lamenting his station one day, he suggested there was a job opening up as a jockey's valet that he might like. And just like that, the next 30 years clicked into place like a Lego brick.

He saw everyone and everything pass through in those 30 years. He laid the silks out for the first home in 13 Grand Nationals, pulled the boots and breeches off countless Cheltenham festival winners, sent everyone from Francome to Dunwoody to Scudamore out to greatness. One day in Stratford he saw a slight young kid wandering around the weighing room looking for a spare pair of boots, having forgotten his own. Buckingham found him a pair but gave the kid a warning. "They belonged to Peter Scudamore, son. You'll never fill them as well as he did." Tony McCoy just smiled and said thanks.

His years as a valet gave him much more satisfaction than his career in the plate ever did, those nine minutes and 49 seconds in 1967 apart, of course. "I wouldn't swap that day for anything, I tell you. But I know in my heart that even if I'd never won the National, the valeting was what made me happy."

He'll be there on Saturday, looking out over a race whose folklore owes as much to him as to anyone. And as the race progresses, one of the legs of the BBC's commentary will fall to Tony O'Hehir, son of the man whose legend was made in part the day he stood by a weighing scales and asked what the story was with those black silks with the red strips.

A day to gave hope to the hopeless everywhere.