The SFO inquiry into the Al Yamamah deal was stopped in December 2006 by attorney general Lord Goldsmith.

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Its huge, long-running contract with Saudi Arabia, known as al-Yamamah, accounts for more than a quarter of its pre-tax profits, according to Mr Fothergill.

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She was closely involved in the negotiations that led to the al-Yamamah arms deal, selling British warplanes worth tens of billions of pounds to Saudi Arabia.

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Although Britain had been selling jets to Saudi Arabia since the 1960s, the Al Yamamah contract dwarfed earlier sales to that country, and any since to anywhere else.

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Because the truth is there was a lot of national insecurity bound up in this, what with the alleged involvement in Al Yamamah of such luminaries as Mark Thatcher.

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Mr Wardle said he had taken advice from the "highest levels", including the Attorney General, the Solicitor General and the British Ambassador to Saudi Arabia, before dropping the investigation into allegations surrounding the Al Yamamah arms deal.

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