For most, summer brings a weekly chore. For Malcolm Hemley, armed with an array of 36 mowers, lawns are a labour of love. Serena Mackesy met the blade runner
A Texan is visiting the stately homes of England. One day, he finds himself on a piece of West Country greensward, and a gardener is walking towards him. "Say," he says, "This is the finest lawn I've ever seen. Tell me. How do y'all git a piece of grass to look so green and smooth?"

The gardener scratches his head. "Tis easy," he says. "There's no trick to it at all. Tha cuts it, and rolls it, and cuts it, and rolls it, and cuts it, and tha keeps doing that for 500 years."

This joke encapsulates the British character. It's not as funny as it thinks it is, and it combines two of our national obsessions: the Old Culture getting one up on the upstart New Culture, and bullying grass into perfect submission. Sunday mornings wouldn't be the same without the buzzing of a million mowers shattering the fabled calm of villages. We may have lost our edge in many other fields, but the British lawn remains a world-beater.

Malcolm Hemley's Narnian lawn in Dorset, surrounded by woodland and dotted with splendid topiaries, sweeps up to his and his mother's house, a former gamekeeper's cottage, with the majesty of a tiny Versailles. This lawn needs a serious mower. Fortunately, Malcolm owns 36 serious mowers, all made by the same company: Dennis, a name more commonly associated with the fronts of fire engines and dustcarts.

These huge mid-Brunswick green machines were mostly sold to local councils, and organisations such as the RAF and the Country Gentleman's Association, from the early Twenties onwards. Malcolm Hemley describes them as "the Rolls-Royce of lawnmowers", and is writing a book on their history, complete with painstaking line drawings of all the essential parts.

It's a labour of love, an enthusiasm that Malcolm calls, with a laugh, "the biggest mistake I ever made". Malcolm is the man everyone rings when they want information: he knows more about the machines than the company's current proprietors. "He has people on the phone from all over the country," says his mother, Gwen, "asking for advice, wanting to know where to find bits and numbers." There is, believe it or not, an Old Lawnmower Association, based in Milton Keynes; enthusiasm for the machines is more widespread than one might initially think.

It all started with an impulse buy during the war. Mrs Hemley looks rueful as she recalls her family's first brush with Dennis.

"I was with Malcolm's father. We went to a house sale at Stocks, in Hertfordshire. We wanted something, I can't remember what; not a lawnmower. We weren't supposed to be as far out as that, with the petrol rationing. Unusually for that time, there was a gardener. And he was standing there looking at this mower. I said, `you're busy'. And he said, `No, this is the last time I'll ever see this thing. I'm putting it in the sale.' It came up at about pounds 14. And father bought it."

This was model 5195, made in 1925. "The valve cap had blown out," says Malcolm, "and you couldn't get hold of spare parts at the time. It stood in the shed at home for years before we ever used it. The first year we got the spare valve cap was 1951." Some time later, he came across another Dennis in another sale, and bought it in case the parts could be useful. Two more followed, and before anyone could stop it, he had a collection. The most expensive buy was pounds 175 for model 188; the least, pounds 2, at an auction. The model he actually uses for day-to-day work is a 1947 Z9, with 36-in blades and a 600cc engine, which set him back a princely pounds 2.50.

We stroll across the lawn, Malcolm pausing to pick up stray twigs, to the old Army hospital sheds, originally intended for Suez but never delivered, where the lawnmowers live. Malcolm is a chatty individual you can't fail to warm to, and he has a disconcerting habit of talking about his mowers as "he".

The machines lie quiet under yards of tarpaulin, stretching into the darkened regions of the shed. Unveiled, they don't look like much to me, but Malcolm delivers mantra-like recitations of model numbers, magnetos, valve-caps, koler engines, blade sizes.

"They were literally built like tanks," he says, and pats his first- ever machine, which has pride of place at the front of the line. I've seen men do this before with machines - mostly cars and tractors, the occasional machine-gun - but emotional attachment to crankshafts is something that has always gone over my head.

And then he starts one up. This process involves a lot of stooping and twiddling, going "right" and and adjusting throttle levers to an eighth of an inch. The mower doesn't want to co-operate at first. "He says `I'm old', you see," says Malcolm, "`I've got an E175 engine, which is about 1955.'" Three more cracks of the starter handle, and everything springs into life. Gleaming gear-shafts rattle, the fuel tank leaps from side to side, everything is in motion with eccentric vivacity.

He throws the gear lever, and the roller whizzes round, dragging blades and grass-box forward at an alarming lick, eating up the land.

Malcolm races behind, under the monkey puzzle, along the side of the drive, manhandling this 6-cwt monster like a Flymo. His face is a picture of calm and enthusiasm, and suddenly I see the point myself. All those old blokes, the head gardeners and the under-gardeners, over all those years, had found their own form of Zen.

And what's more, if you keep on cutting and rolling for 500 years, you've got the makings of a garden.

Malcolm Hemley's collection of Dennis lawnmowers is featured on `Mad About Machines', Channel 4, on 3 April at 8pm. The Old Lawnmower Club (01908 316222).