There were calls for his resignation as chairman of the Commons select committee on defence in 1990, when, on the eve of Iraq's invasion of Kuwait, the members' interests select committee criticised Mr Mates for failing to declare properly his association with Link Miles, a key supplier of flight simulators to the RAF.
Three months earlier, Mr Mates resigned as an adviser to SGL Defence Ltd, a lobby company that specialised in helping manufacturers secure MoD contracts, following suggestions of a conflict of interests with his select committee role.
Michael Mates had no early interest in politics, only joining the Young Conservatives at school 'because they had dances and you could put your arm around a girl'. He spent 20 years in the Army, rising to the rank of lieutenant- colonel in the Queen's Dragoon Guards. In 1974, he was selected from 380 applicants for the safe Hampshire seat of Petersfield, but, as a serving officer, was not a party member. 'If you choose me, I'll join,' he promised the selectors.
His political career never recovered from the part he played as campaign manager in William Whitelaw's failed bid for the Tory leadership in 1975 against Margaret Thatcher. During the early 1980s, he attempted to claw his way back into favour by becoming an unofficial government spokesman, loyally popping up whenever the party failed to field a minister. He went on television in 1984 to defend wholeheartedly the sinking of the Belgrano and later accused Clive Ponting, the civil servant who leaked classified details of the sinking, of 'lies and deception'.
He grew so close to Michael Heseltine during the Westland crisis in 1986, that when he led the poll tax rebellion in 1988, many ministers mistakenly saw Mr Heseltine as the chief architect of the revolt. Any prospect of office under Mrs Thatcher had long since faded by the end of 1990 when he materminded Mr Heseltine's leadership campaign. Though ultimately unsuccessful in securing No 10, Mr Mates had proved instrumental in Mr Heseltine's return to cabinet.
On his appointment as security minister at the Northern Ireland Office following the last election, Mr Mates promised to 'get hold of the terrorists who are causing this mayhem and carnage'.
That robust entry into the porcelain world of Ulster politics succeeded in provoking criticism from both unionists, who spoke of 'unhelpful prejudices' (he once served as a soldier in the province), and nationalists, who described him as 'a Colonel Blimp-type figure'.
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