Sir Mark Thatcher: Mumsy's Boy

"Save me, Mummy", read a placard hanging from a window opposite Cape Town's High Court last week. Sir Mark Thatcher is not noted for his quick intellect, but if he saw the poster as he left the courthouse, even he could hardly have failed to grasp its message. Baroness Thatcher's wayward son had just got out of his worst scrape yet; a charge of involvement in a Frederick Forsyth-style coup plot that could have landed him in a South African jail for 15 years, and everyone assumed that she had somehow extricated him. It would not have been the first time, after all.

"Save me, Mummy", read a placard hanging from a window opposite Cape Town's High Court last week. Sir Mark Thatcher is not noted for his quick intellect, but if he saw the poster as he left the courthouse, even he could hardly have failed to grasp its message. Baroness Thatcher's wayward son had just got out of his worst scrape yet; a charge of involvement in a Frederick Forsyth-style coup plot that could have landed him in a South African jail for 15 years, and everyone assumed that she had somehow extricated him. It would not have been the first time, after all.

The former prime minister put up the £180,000 bail, freeing her son from house arrest last August. When he was in trouble in the US several years ago, she contributed to a £330,000 out-of-court settlement with an embittered former business partner, who accused him of conspiracy, money laundering, usury, perjury, theft and assault. So it would not be surprising to learn that she had settled the £300,000 fine which Sir Mark was sentenced to pay on Wednesday. That, and a four-year suspended jail sentence, was at the centre of the plea bargain which allowed him to fly out of South Africa the same day. He admitted that he had begun to suspect that a helicopter in which he invested $275,000 (£147,000) might be intended for "mercenary activity", but went ahead with the deal, contravening South Africa's Foreign Military Assistance Act.

He may be 51, greying at the temples and the father of a teenage son, but it seems that he still needs "Mumsy", as he calls her, to pick him up and dust him down. It has long been known that if the Iron Lady had a chink in her armour, it was Mark. Where others, including his twin sister Carol, find him gauche, prickly, abrupt and arrogant - "an ego the size of a herd of elephants and the attention span of a gnat" was one description - his mother's devotion to him has always been unstinting. Lady Thatcher once said that Mark "could sell snow to the Eskimos and sand to the Arabs", but others saw his family name as his only asset. His academic career is quickly dealt with: he left Harrow School with three O-levels, well short of qualifying for university, and departed from his first job, at the City accountants Touche Ross, after failing his accountancy exams three times.

By the time Margaret Thatcher became prime minister in 1979, when Mark and his sister were 26, several failed ventures already lay behind him, including an abortive attempt to break into motor racing. But his brusqueness did not register with the wider public until he went missing on a rally in the Sahara in 1982, the only time his mother was seen to shed tears in public until she left office eight years later. His father Denis - later to accept the hereditary knighthood which passed to Mark on his death - had come to Algeria to help find him, but Mark refused photographers' calls for a handshake. He insisted that he had not been lost, and declined to thank the Algerian rescue team, to the embarrassment of his father.

The prime minister's son seemed nothing more than the subject of occasional amusement in the gossip columns. Things became more serious when it emerged a couple of years later that he had gained a commission on a £300m deal won by the Cementation construction company after his mother had recommended it to the Sultan of Oman. Although he was robustly defended by her, the whiff of scandal made it advisable for him to relocate to Texas. He has not lived in Britain since, and when he asked Sir Bernard Ingham what he could do to help his mother win the 1987 election, her bluff spokesman famously advised him: "Leave the country."

In Dallas Mark met and married the car showroom heiress Diane Burgdorf - apart from Michael, 15, they have an 11-year-old daughter, Amanda - but controversy continued to cling to him. A security alarms company, of which he was a non-executive director, went bust, with the US authorities claiming that it owed $1.7m in taxes, though he was later cleared of any liability. Then his partner in an aviation fuel company sued him, leading to the settlement. Most damagingly of all, he was accused of exploiting his mother's name to gain a £12m commission on the giant al-Yamamah arms deal with Saudi Arabia. Senior aides subsequently admitted that if the suspicion had surfaced while Lady Thatcher was still in office, she could have been forced to resign.

By 1995 it was time for another fresh start, this time in South Africa. The family moved to a mansion in Constantia, the wealthiest suburb in Cape Town, but again he was cold-shouldered by local society, failing to gain membership of the Royal Cape Golf Club, and again his business ventures led to trouble. In 1998 a scheme to lend money to poorly paid policemen collapsed amid allegations that it was virtual loan-sharking, leading Mark to complain that he had only been trying to help. "The reality is that he has no business judgement, and he will do any deal with anyone to make money," said Mark Hollingsworth, author of Thatcher's Gold: the Life and Times of Mark Thatcher. "He was always an accident waiting to happen."

Now that accident has duly happened. Thanks to his association with adventurers such as Simon Mann, the former SAS officer jailed in Zimbabwe for his part in a failed coup in Equatorial Guinea, and Mann's chums among South Africa's apartheid-era special forces, Sir Mark has a criminal record. One source called him a "minor player" in the whole affair, "a special forces groupie who got too close".

But the big players were out of the reach of the South African authorities, who were anxious to show that they no longer tolerated the activities of "neocolonialist" mercenaries. That made Lady Thatcher's adored son their sole target. It was the ultimate irony for a man who had always traded on little more than his mother's fame. Her reflected lustre now became a curse: arrested the day before he was due to return to Texas with his wife and children for yet another new beginning, Sir Mark faced the prospect of years in lonely, though luxurious, exile while South Africa's prosecutors painstakingly built their case against a suspect with an internationally recognised name.

The episode at least appeared to have instilled a little humility; during a series of court appearances in November, he made great efforts to remain on polite terms with the press, even deploying some self-deprecating humour. The strain emerged, however, in a magazine interview. With his passport impounded and his phone calls and emails monitored, he lamented, "I will never be able to do business again." When his mother came to spend Christmas with him, his bail conditions prevented him from meeting her at the airport.

Was it Lady Thatcher who persuaded her son that the only way out of his impasse was to plead guilty? She was not mentioned by Sir Mark on Wednesday, when he said on the steps of the court: "There is no price too high for me to pay to be reunited with my family, and I am sure all of you who are husbands and fathers would agree with that." Asked on a South African phone-in programme whether the affair had damaged Mark's reputation, a British pundit had to explain that the reason he had taken refuge there was that his reputation was already in tatters everywhere else.

Although he emerges from each imbroglio more tarnished than before, his mother has never wavered in her support. That will not change now, despite the worst battering the family name has ever suffered. Her only sorrow is that the rest of the world's failure to see Mark as she does will keep him thousands of miles from her side.