“He came from nowhere,” a senior official said at the time. “None of us had ever heard heard of him.”

Well, they have now. Michael Robert Alexander Brown was born on April 19, 1966, into a Glasgow family. His father, Ian, was an executive at one of Scotland’s biggest whisky producers. But his mother, Patricia, told The Times that she had not spoken to him for many years and wanted little to do with him. “Let me just say that he has certain character flaws, and leave it at that. He is not someone that I know very much about these days,” she said from her bungalow in East Lothian.

Mr Brown angered his family by getting into a financial scrape in 1995, when his mother received a telephone call from Naples, Florida. A family friend said: “She was told that Michael had been arrested for writing a number of bad cheques. He had to be bailed out, or he was going to be charged and possibly jailed.”

His father, who had a home in the United States, came to the rescue by paying off the bad debts. Yesterday Mr Brown freely admitted to his error, saying that the sums involved amounted to less than three grocery cheques of about $40 each. It was a misunderstanding and he had paid his father back with interest.

Speaking to The Times from an airport yesterday, he asked for his family’s privacy to be respected. “My mother and I are two completely different people. I love her but we don’t see eye to eye. As my dad used to say, God gives us relatives, so thank Christ we can choose our friends.”

He does not belong to the Liberal Democrats and, despite his massive donation, said that it did not occur to him to register as an overseas voter (he lives in Majorca) at the most recent general election.

But the fast-talking, pony-tailed Mr Brown wants people to understand his motives for giving the money. He said: “The Lib Dems are probably the closest I can get to my politics. I was told how much Labour and the Conservatives spend at elections and wanted to even it up.

“There was no personal interest in this. I don’t want to sit in the House of Lords because I’m too undiplomatic — I shout and scream at people. But no party should be denied power because of money.”

He has made a lot of money in recent years after a patchy early business career that included stints in music promotions, public relations and model agencies. “It was real estate that did it really,” he said. “And since then it’s been in the financial markets — I’ve got a knack of being able to play them. I’ve flown by the seat of my pants most of my life and I rely on gut instinct.” How much is he worth? “I’m not telling you, ” he said. “In excess of £10 million.”

His present enterprise, 5th Avenue Partners, is based in Zug, a medieval Swiss city known for its fruitcakes and, latterly, as a tax haven for the rich.

On June 28 last year, soon after the Liberal Democrats scored well in local elections, Mr Brown set up 5th Avenue Partners UK. It is this entity that is recorded as having made the donations to the Liberal Democrats.

Lord Razzall, the campaign director of the Lib Dems, was vague when he announced details of the donation after the election. The company, he said, was “something in the derivatives world”. In fact it was set up to handle Mr Brown’s investments in Britain.

This week, after a series of telephone calls to the company’s offices in Upper Brook Street, West London, went unanswered, The Times paid a visit. The only person present was Mark Ellis, listed along with Mr Brown as a director of the firm. He said: “I’m just manning the fort.”

Mr Brown accepts that many people might regard such activity as less than might be expected from a business with so much spare cash. He appears genuinely angry with the Lib Dems for failing to make proper legal checks and is cross that the party refuses to tell him how his money was spent. He said: “Their attitude seems to be: ‘Thanks very much for your money and goodbye’.”

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