The sky's the limit

He sits in one of the spacious rooms at Wytham Abbey, the magnificent Gothic structure that he has made his family home, and sets out his plans to revolutionise air travel.

Nothing as trivial as a new Oxford to Cambridge service from Oxford Airport or even a new trans-Atlantic passenger service. No, when Mr Stewart throws himself into a scheme, the sky is barely the limit.

Lying on a coffee table in front of him is a glossy brochure packed with images of airships. Some appear to resemble the ill-fated Hindenburg in scale. But for Mr Stewart, airships represent a safe, clean and highly profitable future.

For almost ten years now he has been quietly working to raise millions of pounds to get at least one giant airship off the ground.

After that he is planning to create a fleet of them, floating hundreds of passengers at a time all around the world, along with heavy cargo. Tourism, disaster relief, border surveillance and freight - these new airships, he maintains, will be able to do it all.

To many people, Mr Stewart is best known as a writer of fiction and best-selling tales of psychological suspense. As he warms to his theme about massive helium balloons as a new environmentally-friendly form of air travel, it is all too tempting to believe he is outlining the plot for his next novel.

The longer he talks, however, the more obvious it becomes that this is no flight of fantasy. Mr Stewart, 60, is a man on a mission.

The SkyCat, as the airships will be known, is to be designed and manufactured by Hybrid Air Vehicles, which is developing the airships at the Cardington sheds in Bedfordshire, the home of the UK's airship industry.

Now, after years of trying, Mr Stewart believes he is close to signing a deal with a Far East company that is willing to pump in millions to get the first giant airship into the air.

The fact that Mr Stewart was able to get Oxford University to part with such a magnificent historic village manor house on the western edge of Oxford, is in a way testament to his single-mindedness and powers of persuasion, laced with old-fashioned Oxbridge charm.

Yet for all his impeccable good manners, it would be a mistake to regard him as a business innocent. His impressive CV may show success as an academic and author, but there has been plenty of dabbling in business down the years and learning "in the field".

He started as an assistant to the director of Mobil Oil before attending the Fontainebleau Business School in France.

Since then there has been trading in bankrupt stock, including one unhappy venture to ship camp beds to Muslim pilgrims bound for Mecca. Sadly, the shipload arrived after the pilgrims.

And there have been various financial venture capital projects for high-tech industries, one backed by the racing driver Graham Hill.

But this time a passion for lighter-than-air technology has carried him to dizzying new heights of entrepreneurial ambition.

Although Michael was a classicist at Christ Church, science has, in fact, always been a great fascination. "I wrote 12 books over 15 years," he said. "Most of them turned on some development in science. There's always some scientific twist."

His interest in airships was ignited by a conversation with a friend who worked in the oil industry about the difficulty of transporting oil from a remote corner of Turkistan. Working through the various alternatives, he could see no reason why it could not be carried by air.

He quickly learned how far airship technology had advanced after meeting Roger Munk, a designer who has for years been working for an airship comeback.

"People still think of the Hindenburg when you talk about airships," said Mr Stewart, referring to the hydrogen-filled airship that burst into flames in 1937 following a trans-Atlantic flight. "The modern airship is very different."

For a start the airlift is derived from helium, an inert gas, with the aerodynamic lift derived from its hull shape. But what makes Munk's SkyCat different is a hover cushion landing system, that enables the airship to land and take off from virtually any unprepared surface - land or water, desert or snow.

By reversing the hover cushion engines on land, the vehicle is able to suck down and remain stationary. This apparently removes the need for ground crews or handling equipment. The airship's envelope structure, which incorporates a large bag containing helium gas, is made with a heat-bonded laminated fabric and a Mylar film provides the gas barrier. The veteran designer is now president and technical director of Hybrid Air Vehicles, created after an earlier company folded. But the SkyKitten, a fully working model measuring about one-sixth linear scale, had at least made its first flight in 2000. Mr Stewart formed his own company, World SkyCat Ltd, to focus on the massive investment required.

"My ambition is to build up a big fleet and charter them out," he said. "It is a massive opportunity but we have been bedevilled by lack of capital. Somebody has to take that first step. We have got to get one in the air.

"The entry level into this industry is measured in tens of millions. But we are close to the breakthrough with a company in the Far East."

I had gone to Wytham Abbey in the expectation of hearing of his hopes to one day provide commuters with a new link between Oxford and Cambridge. Earlier he had explained why an Oxford-Cambridge run would be an ideal distance for airships travelling at about 100mph.

But it turns out his ambitions soar far beyond even that. The deal, now being negotiated, he told me, would allow four SkyDragons to be built, one at Cardington and three in China.

If you thought the idea of a compact SkyCat sounds simply incredible, its big sister, the SkyDragon, will appear totally fantastical.

The SkyDragon would offer 42,000 sq ft of space, the equivalent of an acre. It could carry some 1,200 passengers or 170 tonnes, with each costing $100m to build.

As I struggle to contemplate the scale of these new monsters of the air, Mr Stewart has moved on to chart how it will be unleashed on an unsuspecting world. First there would be a bid to set a new world circumnavigation record for an airship. He contemplates little difficulty beating the record of 21 days set by the Graf Zeppelin in the 1920s. Then there would be a world tour of the world's major capitals, before waiting for the business to come flooding in.

It is difficult not to be carried on the waves of enthusiasm. Travelling at low altitude would make it a wonderfully green form of transport, with emissions of less than ten per cent of an average aircraft.

With only minor interior modifications, the dragon could be deployed in a full range of relief missions, from combating natural disasters to the control of bush and forest fires.

He describes the massive potential for luxury travel, with state rooms, casinos and VIP lounges and car transport as passengers gaze at the stars above the Atlantic.

As for heavy lift cargo, a low-cost airborne freight service would offer an alternative to slow sea transport. Heavy equipment could be delivered to the world's most remote corners for the oil and gas industry. It could even offer an environmentally- friendly means of transporting natural gas in gaseous form direct from well-head to user terminals.

The arrival of his wife, Martine, provides the chance of a pause for breath. Monkey Shines, one of Mr Stewart's books was turned into a feature film in 1989 and he has been involved in various television dramas, usually about science-minded sleuths. Now his wife, formerly head of marketing at Blackwell's, is embarking on a television costume drama about a woman who lives through the English Civil War in Oxford.

He, meanwhile, is planning a television series, typically looking to the future. It will involve various eminent political and scientific figures, offering an imaginary history of the 21st century.

The idea is to ask people like the former American vice-President Al Gore and the Oxford scientist and best-selling author Richard Dawkins what they think the future holds and then turn it into a dramatised history. It will be interesting to see if anybody mentions airships.

But in any case it should not be very long now before Mr Stewart emerges either as a visionary, prepared to risk ridicule, in order to pursue the boldest of entrepreneurial dreams, or a writer, whose imagination has spiralled way out of control.