So it is no surprise that aspects of the biggest of them all, the pounds 20bn Al-Yamamah agreement with Saudi Arabia, should come back to haunt the Conservative Party. The story appears to be simple. As Prime Minister, Margaret Thatcher threw herself enthusiastically into securing the deal for Britain; her son, Mark, whose main qualification was his access to his mother, gained himself a role as an intermediary, and emerged with a cut of pounds 12m.
Mrs Thatcher was right to do her best to win a deal that is reckoned to have secured 20,000 jobs in Britain's defence industry until the end of the century and the future of a very important company, British Aerospace. But she was wrong to have allowed her son to become involved in a deal that was to transform him into a multi-millionaire. No one can be sure how much she knew about the extent of his involvement. But there can be no doubt she was well aware of his role: at one stage Sir Clive Whitmore, permanent under-secretary at the Ministry of Defence, was asked to tell her that her son's activities were threatening the negotiations.
Both the Pergau dam and Matrix Churchill affairs revealed the Government's readiness to break its own rules, whether they concerned the separation of trade in arms from development aid or compliance with sanctions on Iraq. It is now seems that Mrs Thatcher broke the rules again over Al-Yamamah. Official guidance in Questions of Procedure for Ministers, the handbook on government ethics, says there should be no conflict between ministers' private interests and public duties. Furthermore, a ban on gifts that could place a minister 'under an obligation' extends to family members.
The present Government should draw the right moral. Big arms deals involve security issues, and their details are necessarily largely confidential. That creates an overwhelming need for proper behaviour. Rifts are liable to take place when rules are broken, as happened with Malaysia over Pergau. The row over Mark Thatcher will damage relations between Britain and Saudi Arabia and embarrass the Conservatives as they meet in Bournemouth. The family values revealed are not the sort that the Government is trying to promote.