The thing about inventor types is that they view things differently to us humans. And so this reporter's jumper is not merely pink but, as James Dyson explains, it is the "exact same shade" that featured on the first ever bag-less Dyson vacuum cleaner the entrepreneur designed.

Later, he confides that he is not too fond of the carpets in Dublin's Merrion Hotel (where I interviewed him) but pauses, although he is half an hour late for his next appointment, to admire at close range the plasterwork on the window shutters. The room is in a Georgian building that was the birthplace of the Duke of Wellington. "He was a very clever man," muses Dyson.

This almost obsessive attention to detail has stood the man who sells £500 million worth of vacuum cleaners across the world in very good stead. It definitely contributed to his by now legendary Eureka! moment in the late 1970s when he discovered that vacuum cleaner technology could be drastically improved by getting rid of the bag.

Now, the 53-year-old design engineer is literally cleaning up.

"I was vacuuming at home at the time," he says still managing to inject enthusiasm into a story he must have told hundreds of times before. "The vacuum cleaner wasn't picking the dirt up, so I changed the bag but it still didn't pick up properly even with an empty bag."

While other people had for almost a century accepted their suction-less lot, not Mr Dyson, who at the time had his new wheelbarrow, the ball-barrow, in production. He took the machine apart to find out why it would not pick up the dirt.

He patiently explains what he established. Traditional vacuum cleaners have bags with tiny pores which are used to trap dust, but still allow the air to pass through. What actually happens though, Dyson discovered, was that the dust very quickly blocks the pores obstructing the airflow and reducing the suction power.

Amazing but not quite Eureka. That moment didn't occur until he realised that the cyclone technology used to clear up dust in his ball-barrow factory could solve the suction problems of the vacuum cleaner.

"The very first prototype was very crude and made with a length of hose and a cardboard cyclone. It was very Blue Peter but it worked," he said.

A graduate of the Royal College of Art, Dyson could be Nigel Havers' twin, such are the physical similarities he shares with the British actor. He possesses the same quintessentially English manner, and even if the phrase doesn't flow quite as smoothly as the colourful Dyson Dual Cyclone, he seems genuinely, er, passionate about vacuum cleaners. He laughs as he concurs.

After spending five years in his garden workshop developing his idea, and when he had the product he wanted, his next problem was trying to find someone to license the Dyson.

"If companies did give me a reason why they weren't going for it, which they often didn't, they would say they couldn't believe that if the technology worked the big companies wouldn't have already come up with it," he recalls.

In 1985, he secured a licence in Japan - the US licence a year earlier was terminated shortly afterwards leading to Dyson taking a patent infringement lawsuit against the company. The original machine, the G Force, didn't look exactly how Dyson had envisaged it. "They had smoked as opposed to clear glass on the front so it you couldn't see the technology and the glory of the dirt. I wanted people to think, I got this nasty stuff off the floor and into the Dyson," he says.

After winning various design awards, the Dyson DC01, made to his design at his own research centre and factory in Wiltshire, arrived on the market to the consternation of the big vacuum cleaner companies. Soon, the business pages were shouting about vacuum wars and the Dyson began selling 10 times more than its nearest competitor.

What is truly remarkable about James Dyson's story, which is told in his ghost-written autobiography, Against The Odds, is that it spawned a new way to bring a product to the market. "People started calling it Doing a Dyson," he says. The concept led to an exhibition on Doing a Dyson or "how to invent new technology, manufacture it yourself, market it yourself and topple the market leaders". Easy peasy, apparently.

His company - a place where suits are frowned upon and each employee makes a Dyson themselves from scratch to take home on their first day - has up till now been mainly a one product wonder but the fruits of more of Dyson's Eureka! moments will be manufactured in the future. James Dyson looks genuinely sorry that he can't say more but he chats easily about his wife and three grown up children. Oh and the money.

"I don't even have a Rolex," he says, denying a flash lifestyle by pointing to a rather humble looking £25 watch. He thinks hard when asked about any indulgences. And then, he says: "My stone collection."