Thatcher went on crash diet ahead of poll win

The programme, which included up to 28 eggs a week, promised to help the future Prime Minister shed 20lb in two weeks.

A yellowing note outlining the strict regime – released today along with thousands of Lady Thatcher's personal papers – was found tucked inside her 1979 Economist pocket diary.

It was thought she had wanted to get "in trim" for the historic

election campaign.

"It has to be pre-election," said Chris Collins, of the Margaret Thatcher Foundation (MTF). "I think she was looking to get in trim for the cameras.

"She probably thought, 'the cameras are going to be on me the whole time – I'm going to lose some weight'.

"But she is not somebody who had a problem with weight at all. She is on the move the whole time – she burns energy."

As Britain's first woman Prime Minister, Lady Thatcher, now 84, faced different "expectations" to her predecessors, including James Callaghan and Harold Wilson, Mr Collins said.

"Callaghan and Wilson wouldn't have been held to the same expectations she was held to," he added.

The diet included a daily breakfast of grapefruit, one or two eggs,

black coffee or clear tea.

Two eggs were served in each of her week day lunches, while steak, lamb chops and fish were the staple of most dinners.

The majority of items were ticked off – but small crosses appeared next to items including eggs and grapefruit on the Monday.

The neatly folded piece of paper, which warned the diet should not be followed for more than two weeks, is headed "The Mayo Clinic Diet".

A spokeswoman for Mayo Clinic, an American-based non-profit making medical practice, said she could not comment on any possible link to Lady Thatcher. But she added: "There have been no official Mayo Clinic endorsed diets until this year."

The official Mayo Clinic diet recommends a common sense approach, with "generous" servings of healthy foods and "lesser amounts" of high calorie dishes, combined with regular exercise.

In an interview with The Sun published in March 1979, Lady Thatcher said she had "no special dieting regime".

She also told the newspaper she wore size 14 dresses and weighed nine-and-a-half stone.

The MTF released Lady Thatcher's papers – covering the period between May and December 1979 – to the Churchill Archive Centre at Cambridge University.

Mr Collins said it was the first time a British Prime Minister's personal notes had been made public during their lifetime. "The papers show what it was like to be at Number 10, rather than just the policy stuff, which, however important, doesn't give the full picture," he said.

They also show Denis Thatcher bemoaned missing a night out with

his "chums" to attend an official dinner.

On one occasion, the Prime Minister's husband was forced to forgo "probably the best rugby dinner of this year" to attend a black tie reception at London's Claridges Hotel.

The event, hosted by the President of Indonesia in honour of the Queen, was held on November 15 1979 – the same night as the centenary dinner of Middlesex Rugby Football Club.

Mr Thatcher, in a note from a diary secretary, is advised of "another dreaded state banquet" and told an invitation has been accepted on his behalf.

"What I do for the Party!" he fires back in his reply. The Indonesian ambassador was later sent a note saying the Prime Minister and Mr Thatcher accepted the invitation with "great pleasure".

Mr Thatcher's mood could have been influenced by the sometimes poor standard of food on offer, the papers reveal.

Following a Number 10 dinner laid on for the President of Colombia in July 1979, Lady Thatcher wrote a Prime Ministerial minute in which she said she was "not all happy" with the standard of cuisine and demanded improvements.