Margaret Thatcher has rarely expressed regrets. Like President Bush, what opponents consider her intolerable intransigence she has always dressed up as unshakable resolution. She was so eager to distance herself from pragmatists like Edward Heath and Harold Wilson, her predecessors at Number Ten, that she made a cardinal virtue of her ability to arrive at a decision and stick to it, come what may.

Even those who did not like her policies came to admire her perseverance. Yet in the end it was Lady Thatcher’s doggedness that was her undoing.Even when, in rebellion against her hated poll tax, the usually phlegmatic English set fire to Trafalgar Square, quite literally a stone’s throw from her tied cottage in Downing Street, she still could not bring herself to change course. Before long her Cabinet took it in turns to tell her she was finished.

There is one regret, however, which Lady Thatcher does admit: She did not spend enough time with her young children when setting out on her political career. It is chilling proof of her determination to succeed that, in the maternity ward awaiting twins, she signed up for her bar final exams to ensure her resolve once the children were born. This rare sense of remorse continues to inform her uneasy relationship with her offspring, Mark and Carol.

Whereas Carol is a warm=hearted woman who appears to have inherited all the best of Lady Thatcher’s mother, Beatrice, Mark proved to be a problematic child, more akin to Thatcher’s dutiful husband Denis. While Denis avoided speaking to the press — I possess a four-page note in his own hand charmingly expressing his preference not to be interviewed — Mark was considered such a potential liability to his mother’s prospects that he was sent into exile abroad for the duration of every general election in her time as a conservative leader.

Mark has become a figure of fun to the British, who have eagerly followed his antics, from affecting to be lost in the desert during a car rally — an event which prompted public tears from his distraught mother — to his business and marriage troubles in Texas and South Africa. “The Wonga Coup” (Public Affairs, 304 pages, $26) by Adam Roberts, about a failed coup in Equatorial Guinea in which a bunch of incompetent British mercenaries took the lead, would likely not have found a publisher had it not promised to disclose Mark’s part in the often comic shenanigans.

Unfortunately, this ill-written, poorly researched, half-baked account tells us little we did not already know. There is a great deal about the background to the coup, much of which may be true, though the material about the coup itself is turgid and barely digested. As well, Mr. Roberts also tries to fancifully link the events to Frederick Forsyth’s thriller, “The Wild Geese,” in which fiction and fact may (or may not) have been intertwined. But when it comes to the kernel of our interest — Mark’s involvement — there is precious little.

If the troublesome son of Britain’s favorite conservative heroine put up the money for the rental of a helicopter knowing it would be used in the coup, there is no evidence of it here. In three interviews with Mark, Mr. Roberts appears to have discovered nothing new. But then he writes that he never actually managed to visit Malabo, the scene of the coup, either. Having admitted he was repeatedly denied a visa, so “I would never be allowed into Malabo,” Mr. Roberts goes on to explain that “after Malabo, the hardest place to conduct interviews was Harare.” Which, considering that he conducted no interviews in Malabo, because he didn’t visit there, has very little meaning.

The book’s aim, it appears, is for Mr. Roberts to express his sneaking regard for the soldiers manqué while simultaneously taking a swipe at the old country they, including Mark, have long deserted. While he is suitably wide-eyed about passing on tales about the superannuated rogues, Mr. Roberts singularly fails to grasp the social milieu they come from. Eton is not, as he claims, “the country’s most prestigious public school.”That would be Winchester. Further, he describes Eton as a place, “where ministers and future royals were caned.” No member of the royal family attended Eton until Prince William, and he was never beaten. Nor is White’s London’s most exclusive gentlemen’s club; that would be the Garrick. And, as any duke will tell you, at White’s they most certainly do not throw bread rolls. And so on.

“The Wonga Coup” is a missed opportunity. Evelyn Waugh, in “Black Mischief” and “Scoop,” Graham Greene in “Heart of the Matter,” “The Human Factor,” and others, even John Le Carré in recent thrillers, have taken similar African material and spun it into gold. Most disturbing, perhaps, for those who rely upon the Economist for their weekly briefing, is that for four years Mr. Roberts was the magazine’s Johannesburg, S. Africa, bureau chief. As Mark Thatcher might say, “Crikey!”