Baroness Thatcher may be considered a little elderly to make her debut as a Vogue model at the age of 82. But the former Prime Minister, whose portrait appears in the July edition of Vogue magazine, was never one to be constrained by convention.

The image of Lady Thatcher, shot by Mario Testino, adorns an issue devoted to a celebration of the ageless. “True style demands conviction and few women have as much of that commodity as she, as we think this picture shows,” the magazine's publicity gushes.

Her public speaking days are over, on doctors' orders, and there is no expectation of a new volume of memoirs but as the portrait proves, Lady Thatcher remains a potent force.

David Cameron, emboldened by his recent election successes, invoked her memory in a claim that the Conservatives would return Britain to “good housekeeping” earlier this month.

Even Gordon Brown felt the need to invite his predecessor for tea, served in her old office in No 10, soon after becoming Prime Minister. Close friends concede that her health is failing and that she has been taken to hospital several times in recent years. On each occasion, however, she has been discharged swiftly.

Her work now is confined largely to the maintainance of the Margaret Thatcher Foundation.

One of the most famous portraits of Lady Thatcher was by Helmut Newton, who was commissioned by the National Portrait Gallery in 1991.

Newton, who died in 2004, said in his autobiography that he had a “kind of crush” on the former Prime Minister. He said that on the day of the shoot in Anaheim, California, “I asked her to please look serious. She replied, ‘Oh, but one looks so disagreeable when one does not smile'.”

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