One of Margaret Thatcher's most trusted advisers urged her not to stand for another election after she overcame a disastrous campaign to secure a third successive term in office.
Private secretary Charles Powell described the level of abuse ahead of the 1987 vote as "unbelievable" in an intimate note to the prime minister, and told her: "It's not right that you should be subjected to a further round like this time."
The letter, signed "with affection and respect" by Lord Powell and his wife Carla, has been published in full for the first time as part of the latest release of Lady Thatcher's private papers.
Lord Powell said he had only remembered writing the private letter when extracts were published in Charles Moore's biography of Lady Thatcher.
Ahead of its public release, he said: "It's an unusual letter for a civil servant to send a Prime Minister even on a very personal basis, reflecting the size and intimacy of Number 10, especially in those days."
Chris Collins, who is a historian of the Margaret Thatcher Foundation and helped write the former prime minister's memoirs, said those who worked with her felt "very protective".
The papers also revealed that Lady Thatcher was briefed on The Sex Pistols ahead of an interview with teen pop magazine Smash Hits and warned: "You may not enjoy this." She was urged to appear "confident and relaxed" while navigating questions on contemporary music in a bid to appeal to the youth.
Meanwhile a "mystery starter" made from beef consomme, cream cheese and curry powder had been revealed as one of Lady Thatcher's go-to recipes. Her recipe for orange and walnut cake, "lamb chops in a parcel", and stuffed "courgettes maison" served with prawns and mornay sauce, are also included in the file.
The Margaret Thatcher Archive Trust is gradually overseeing the release of her private files through the Churchill Archive Centre at Cambridge University.
The public can browse the archive via www.margaretthatcher.org.