You would not now know anything had been wrong

Friend of Lady Thatcher

It happened during a holiday late last year when the 76-year-old and her husband, Sir Denis, were celebrating their golden wedding anniversary on Madeira.

The alarm was raised by Sir Denis after she developed problems with her co-ordination and her speech became slurred.

He was at her bedside as she stayed in a private room of a hospital for two days and they extended their holiday to allow for some extra rest.

A close friend said she made a "very good recovery". Only the Thatcher's' closest friends and children, Carol and Mark, knew what had happened.

Workload remains

The friend said: "You would not now know anything had been wrong. It was a very minor stroke and she remains as energetic as ever."

The Conservative leader, Iain Duncan Smith said in a statement that he was sorry to hear Lady Thatcher had been ill but was delighted she had made a full recovery.

There are few signs Lady Thatcher is reducing her workload as a result of the stroke.

Since returning from Madeira she has been active in the House of Lords and on Wednesday represented the Queen at Westminster Abbey for the memorial service for Lord Hailsham of St Marylebone, the former Lord Chancellor, who served in her cabinet.

She has five lecture tours planned for the United States and in the spring her new book Statecraft is due to be published.

Lady Thatcher is not known to have suffered from any serious health problems before, although in 1994 she collapsed while making a speech in Chile due to a stomach upset.

Britain's only woman prime minister, she was in office from 1979 until 1990 when she resigned after losing the confidence of her party.