Leading Article: Mark: the truth will do

WE HAVE seen it so often before: over the Pergau dam, over Lord Archer's share dealings, over arms to Iraq, over MPs receiving fees for placing parliamentary questions and now over Mark Thatcher's role in the Al Yamamah arms deal. Shoulders are shrugged. ('It's a wicked world, old boy. That's how things are done. Goes on all the time.') Waters are muddied. ('National security, you know. Jobs at stake.') Conspiracy is alleged. ('Why have they printed it this week, when it's our conference. Tell me that, eh?') The right to privacy is upheld. ('What has your editor got in his bank account? Wouldn't tell me that, would he?')

Never explain, never apologise. By following this simple rule, the Tories have succeeded in defusing a long series of potential scandals. They calculate, with some reason, that both press and public will quickly become bored, that one week's sleaze will be overtaken by the following week's royal adultery. And they manage to imply that, in any case, we have no business questioning the conductof our elders and betters.

What isextraordinary is that the Tories have apparently no conception of how sleaze undermines the whole basis of the philosophy they profess. The justification for Thatcherism was that it supposedly rewarded honest, entrepreneurial endeavour. If a man makes millions for no better reason than that he is the prime minister's son, if ex-ministers become directors of the companies they have helped to privatise, the market economy becomes what its fiercest critics always said it was: a means for allowing unscrupulous people to enrich themselves. In the same way, Soviet communism was undermined once it became clear that it allowed those who ran the state a privileged lifestyle. Ideologists must expect to be judged by their own high standards.

Questions about Mark Thatcher have festered for a decade. How did he come by a fortune estimated by some to be as much as pounds 40m? If he were just an ordinary failed accountant nobody would be more than mildly curious. But he is not. He made his money while his mother was Prime Minister, lecturing the rest of us about the virtues of hard work and thrift and insisting that the only jobs worth having are 'real jobs'. He has persistently refused to give even the faintest clue about the nature of his sudden success. Now, it has been alleged that he acted as a middleman in the Al Yamamah deal between Britain and Saudi Arabia. Nothing wrong with that: the deal, after all, was potentially worth pounds 20bn to Britain and secured 30,000 jobs at least until 2005. Even if, as the Ministry of Defence seemed to think, he was actually getting in the way, Mr Thatcher could be forgiven a patriotic wish to assist. Nothing wrong, either, perhaps, if he received some recompense for his time and trouble. But pounds 12m?

As always, there are denials. On closer inspection, these look more like evasions. 'I haven't even sold a penknife,' Mr Thatcher has said. But nobody has actually accused him of selling arms, only of helping to fix a deal. Baroness Thatcher, according to a statement from her office, is 'absolutely satisfied' that the deal was 'properly negotiated' between the two governments. But again this is not quite the point at issue.

Why can't we be told the truth? Because, it is said, arms deals are always complex and murky and, Middle Eastern governments being what they are, all sorts of 'commissions' have to be paid. Saudi sensibilities will be offended, the present deal cancelled and thousands thrown out of work. In any case, details of discussions between the two governments were confidential and, if Britain broke faith, this would jeopardise future business not just with the Saudis but with other countries. All this is true and helps to explain why Whitehall rules, dating back to 1919, require ministers to ensure that their private interests and those of their families are kept separate from their public duties. Lady Thatcher should have made every effort to see that her son did not profit personally and substantially from the Al Yamamah deal. And, even now, that remains the only important question. It should be possible, without delving too deeply into Saudi Arabian 'business practices', to mount an inquiry into the Thatcher family's behaviour. This should tell us how much Mark Thatcher received from the deal; what his mother knew about it; what attempts she made to put a stop to it; and the extent to which she breached the Whitehall protocol on conflicts of interest. What is at stake here, more than Lady Thatcher's rapidly rusting reputation, is Britain's equally corroded faith in the probity of public life.