Sir Alan Sugar: would you like sugar with that?

Thanks to the power of television, Sir Alan Sugar is the most recognisable face of British business. He's one of the most recognisable on British television. The fourth series of The Apprentice, the hit show he presents, will begin on Wednesday, adding to his already extraordinary public profile. But he remains, to a surprising degree for someone who has spent several decades in the public eye, an enigma.

Once again, we have ourselves a fresh batch of 16 apprentices putting their hopes on the line. Yet the question that intrigues many of us more than what will happen to them is: who exactly is this great sorcerer whose secrets they aspire to attain? Is he really a visionary futurist, a rune-reading technology mogul with an all-seeing eye for a fast profit? Or is he a grumpy old dinosaur who hankers for the old days and feels threatened by women?

Unfortunately for him, his on-screen image does not correspond very closely to his real persona. "I don't like it that much," he moaned recently in an interview arranged to publicise the programme. "We actually do have quite a bit of humour when we're filming, but the BBC has categorised me as Mr Nasty. That's what they want, so all the humour ends up on the cutting-room floor."

Given his surname, that was a gift to the headline writers ("The sweeter side of Sugar" etc), but there was something slightly saccharine about the tycoon's tear-jerking tirade. In reality, he is a bootstraps-tugging tough guy – and always has been. When he was later questioned over the importance of employment rights at a press conference called to launch the new series, he barked: "If they don't like it they can piss off. It's as simple as that." He is not one for "human rights rubbish", Sir Alan.

What we do know is that this son of an East End tailor has an innate gift for making money. When he was a schoolboy he was flogging photographic film to his pals and boiled beetroot to the local greengrocer. He left school at 16 and began selling car aerials and electrical goods, setting up Alan Michael Sugar Trading 40 years ago, at the age of 21. Two decades on, Amstrad would be a byword for computer technology in Britain and have a stock market value of £111bn. Though the company later ran into difficulties, it moved into telecommunications and was sold last year to BSkyB for £125m. Sir Alan himself has a personal wealth in the region of £800m.

Despite the occasional flop (such as the recent E-m@iler phone), he has grown from an obscure trader in hi-fi turntable covers into a figure of national importance; the beacon of business to whom Gordon Brown has turned for advice in how to encourage new generations of entrepreneurs. Sir Alan's suggestion has been to offer young people more practical education that will enable them to work with greater expertise on the grill at McDonald's or behind the fish counter at Waitrose, a so-called "Mcqualification" that would count for more in the great university of life than a "meaningless" academic qualification.

Sir Alan has attempted to persuade his BBC colleagues that they should make a teenage version of The Apprentice in order to help what he sees as Britain's molly-coddled youth. "Some of the youngsters today live in a dream world," he said recently. "They're not focused on what they are going to do when they leave education; not focused on the fact they have to support themselves. We want to try to instil some spirit of enterprise into young people."

No-frills Mr Brown likes the cut of Sir Alan's gib. In turn the businessman, in an interview with The Daily Telegraph, praises the Prime Minister for presiding over an "old-fashioned Tory" government and being "like me" with his "strong work ethic". Despite this admiration for Conservative politics, Sir Alan is a Labour donor, giving £200,000 to the party coffers in 2001, and has described Tony Blair as "refreshing".

And there is another apparent contradiction, for though Sir Alan – who turns 61 this week – might like to be seen as dour and frugal like Mr Brown, he enjoys nothing better than to spend his spare time hurtling through the clouds in one of his private planes.

Indeed, when the media celebrity Piers Morgan went to Essex to interview the businessman, he found Sir Alan dressed in a Biggles flying jacket and shades and ushering him towards the airstrip. Up in the skies and grappling with the controls, Sir Alan, the man who made a fortune from technology, disclosed: "I love it up here. Nobody can bother you, there are no phones or faxes or bloody emails."

Within the Sugar empire is Amsair, an executive aviation company which was founded in 1993 and is now run by his son Daniel. Its fleet of Cessnas is used to privately ferry British business chiefs to their meetings.

Sir Alan, Brownite though he might be, has a Rolls-Royce parked at his home in Chigwell, Essex. It carries the number plate AMS1.

He's also quite sporty, being handy with a tennis racket and having been chairman of Tottenham Hotspur for a decade. The latter experience was often painful; in fact, he has since described it as a "waste of my life". At first Sir Alan was seen as Spurs' saviour, wiping out the club's £20m debt, but he fell out with his erstwhile ally Terry Venables, the club's manager turned chief executive. The dispute became so acrimonious that Venables was forced off the board and out of the club in 1993, though he was later to enjoy a spell as a national hero, managing England in the 1996 European Championships.

Sir Alan soldiered on at Tottenham's White Hart Lane, hiring a succession of managers including Osvaldo Ardiles and George Graham but finding success on the field elusive. In 2001, exasperated by his efforts and disgusted by abusive fans who had turned against him, he decided to call it a day.

A winner such as Sir Alan rarely steps away from the table before he is ready. But Venables is certainly not the only high-profile figure to have been critical of him. The late Sir John Harvey-Jones, the former chairman of ICI and a previous incumbent of the role of Britain's television business guru with shows such as Troubleshooter, took against Sir Alan's presenting style. In an interview with Management Today in 2006 he said: "I never liked Alan. I always thought he was a bully. His values are in my view totally irrelevant to the needs of business. I watch his programme with horror. If I had behaved that way for one day at ICI, I'd have been hot-stuffed and rightly."

Some of those who have appeared on The Apprentice have been similarly disparaging. Syed Ahmed, who took part in the second series, suggested that the image the show gave of Sir Alan sitting atop the business world, dispensing nuggets of wisdom, was misleading. "The show is 100 per cent PR for Sir Alan, because the reality is nothing like what's portrayed on television," he told the Daily Mail. "Through careful editing, the BBC created the image that his offices are in a gleaming building in Canary Wharf. But go to his HQ, which is actually in Brentwood, Essex, and see the reality for yourself. It's like a ghost town. There's no air conditioning and I haven't seen toilets like that for years."

Apparently it's not just Sir Alan's sense of humour that has been rather cruelly left out of the final edit.

Another contestant, Katie Hopkins, landed Sir Alan in controversy last year when he questioned whether she would be able to cope with a job at Amstrad when she had two young children at home in Devon. Hopkins bowed out of the show and the TUC weighed in by saying The Apprentice was sending the wrong signals to employers over the hiring of female staff.

Seemingly in search of some similarly explosive scenes, the programme-makers have this year selected as a contestant Shazia Wahab, the veteran of a £1m sex and race discrimination claim against her former employers in the City. But Sir Alan isn't about to be born again as a champion of political correctness. His questioning of Hopkins was a legitimate way of seeking a solution to a real workplace problem, he argues. Besides, the present maternity laws mean "people are entitled to have too much. Everything has gone too far," he told the Telegraph. He has been even more blunt (and unrepeatable) about the rights of Heather Mills.

As for those commentators who criticise his show as being used by the BBC as a shallow substitute for more substantial business programming, he is unflustered, suggesting that the programme is not a guide to running a FTSE-100 company, but a "recreational" activity.

Sir Alan, who owns a large property portfolio through the investment company, Amsprop, has made his money and has little to prove. He recognises The Apprentice for what it is. The show demands he performs a role rather like that of Britain's other TV Mr Nasty, Simon Cowell, who is also no slouch in the world of business, having amassed a personal fortune in excess of £100m.

"Mary Poppins I am not," is Sir Alan's catchphrase for the new series. Well, obviously Sir Alan. But even though the sound of him can be something quite atrocious, his is an East End story that's Supercalifragilisticexpialidocious.