It is mid-day in the Museum of Gardening. Clive Gravett, the founder, curator, and owner of a majority of the exhibits, is pondering the peculiar nature of engineering genius. "With a lot of inventors, they've got the mind so that when they get a problem, they just want to solve it," he says. "It doesn't matter what the problem is, so you never know what they're going to explore next."

This is a favourite topic of Gravett's, and today it has been prompted by a relatively minor part of his collection: a glass tube, about a foot long - "blown glass," says Gravett, leaning in close, "so it's probably early Victorian." George Stephenson, the 'father of railways' and inventor of a miners' safety lamp, also came up with this: a device for straightening cucumbers. Stephenson's key works are listed on a plaque nearby and they are indeed a bit of a motley, some whimsical, some world-changing. But this museum, located in a corner of a garden center in Hassocks, with Clair de Lune playing over the PA system, interrupted by occasional announcements about growbags, is one of few establishments on Earth where a luminary like Stephenson must stand in the shadow of a much greater historical figure. The Museum of Gardening is a shrine to Gravett's hero, Edwin Beard Budding, who in 1830 made one of the great intellectual leaps of the nineteenth century, and invented the lawnmower.

Much like Einstein's general theory of relativity, If Budding hadn't come up with the lawnmower, we might still be waiting for it. Budding was one of those bright-eyed tinkerers so common in the 1800s - a 'machinist' according to his epitaph. According to legend, he was sat one day at a cloth-cutting machine, watching the way in which a bladed cylinder travelled over the material, cleanly removing the nap as it went. He glanced out of the window, where men were working a lawn with scythes, and he had a sudden moment of inspiration. Surely this cutting cylinder could be used on grass as easily as cloth?

In that instant, the lawnmower was born. "And it has barely changed to this day," explains Gravett, a thin, sinewy man in his early sixties, with icey blue eyes that turn to liquid when he gets excited, as if melting through proximity to his enthusiasm. "Compare it to the fine-turf mowers of today, principally it's the same thing. You have a roller, a cutting cylinder, and a drive. That's his design."

Gravett was perhaps destined to fall for Budding. The son of farm labourers, Gravett wanted to follow his father into horticulture. "I wanted to stay on the farm, but my mother said, 'You don't want to end up like us, living on tithed property.' She gave me a bit of a push." Instead, Gravett went into banking and, smart, energetic, and blessed with an unforced quirkiness, steadily rose to the position of branch manager. "Thirty-five years later I was very disillusioned," he says. "The culture. I'd seen a lot of colleagues waylaid by stress, and I thought: No, you're not going to do that to me. We got our branch to the top of the list and I resigned, and accused Fred Goodwin of corporate bullying in my resignation letter."

After leaving the bank, Gravett started up a small horticultural business. He was tending the gardens of a retired solicitor in Ditchling one day when he discovered four old mowers in the garage. "He said he wanted to dump them," Gravett says. "I said, 'You can't just dump them.' I took them, found there was an old lawnmower club, and it went from there."

Gravett is cagey about how many lawnmowers he actually owns, but it's somewhere around 100. That's not bad, he suggests, since the market for antique lawnmowers is hardly pricey, but it can seem excessive given that there is no actual lawn on his own property. Many of his finest lawnmowers reside at the museum, where they tell a simple story: huge and bulky and strangely insectoid in the nineteenth century, with motors coming in around 1904, and the weight dropping until the Flymo arrives in the 1960s, a gorgeous piece of domestic futurism, more manta-ray than machine. "A lot of collectors are quite funny about Flymos," Gravett observes.

Gravett loves to talk about the magic of restoring a lawnmower. "Some Ransomes mowers can be difficult to date," he says, "until you strip the cutting blade back to the metal and see 1907 or 1911, and you're the first person to see that since it was put together." His real passion, however, is the research. It's the research that brought him to Budding.

"In the reading I did around my first mowers, I found several references to Budding." he says. "In Stroud, where he lived, the council had put up a plaque for "Edward" Budding. He wasn't well off so there's no family record." Born in 1796, the illegitimate son of a farmer - "his mother was probably the housemaid." - Budding was a clever child, and went into carpentry and then engineering. Alongside the lawnmower, he invented an early pepperbox pistol, and in the 1840s, a few years before his death, he invented the screw-adjustable spanner. None of these made him much money: they arrived too early, and only took off after his death. His lawnmower was so ahead of its time that Budding had to test it at night; "possibly because of prying eyes," laughs Gravett, "but possibly because people would think he was stupid."

Today, Gravett remembers Budding though his museum and through his charity, The Budding Foundation, that supports young people with education, training and sport. He's still on the lookout for lawnmowers, and urges everybody he meets to check their old sheds for forgotten treasure.

There's one lawnmower he doesn't have in his collection: a Budding. "Nobody has a Budding," he sighs. "He probably made a few thousand, but the two wars gobbled scrap metal. Even so, I like to think one might be found."

Still, Gravett managed to get close to his hero a few years back when he took a trip toDursley in Gloucester, where Budding is buried. "Nobody had written about his grave or where it was, so I decided to find it. I researched the churchyard, and the council provided me with a map to the plots. The border fence had been moved twenty years back, when six graves were taken away. When I found Budding's grave, it was right against that fence. We're lucky we didn't lose him."

The grave, like much about Budding's legacy, showed signs of neglect. It was overgrown and covered with brambles. Gravett lights up at the memory. "I cleared all the brambles off, and then, since I happened to have a 100-year-old lawnmower in the back of the truck, I hefted it over the fence. I mowed as close as I could to his resting place."