In public Margaret Thatcher was the no-nonsense Iron Lady but behind the scenes she turned to lucky charms and dubious health remedies to help her cope with the demands of being prime minister, newly released public papers reveal.

Thatcher’s papers, made public after 30 years, show it was the unlikely figure of Barbara Cartland who came to her aid in 1989, a year when the government’s popularity plummeted as a result of high inflation, the poll tax and rows over Europe.

In November 1989, shortly after the fall of the Berlin Wall, the prime minister lunched with the queen of romantic fiction. She subsequently sent Cartland a letter saying: “Thank you for the Golden Acorn – I shall need it in coming days!”

The nut in question appears to have originated from an oak tree in the garden of Cartland’s estate near Hatfield, Hertfordshire. The tree was reputedly planted by Queen Elizabeth I on shooting her first stag, and Cartland believed it had magical powers.

In a 1994 interview with the Sunday Telegraph, the author related how she had given one of the “magic acorns” to a couple who appeared unable to have children, “and now they have a beautiful bouncing baby”. She added: “Of course, she [the mother] was always taking my vitamins.”

Cartland, the founder of the National Association of Health, took about 100 “all-natural” pills each day, including one made from “crushed sheep’s brain plus heart”, and she supplied Thatcher with some of them, their correspondence reveals.

The author Barbara Cartland, shown here in 1996, supplied Thatcher with some of her ‘all-natural’ remedies. Photograph: Jane Bown/The Observer

In June 1989 Cartland wrote to the prime minister saying: “In case you ever feel tired, I am enclosing the very latest product we have in the Health Movement, which takes oxygen to every part of the body, including the brain. My son, aged 51, says that he wakes up in the morning and feels like a boy of 16.”

A week later, Thatcher, who spent her early years working as a research chemist and who famously claimed to sleep for just four hours a night, replied thanking Cartland for the “nutrimental capsules”.

The following month the prolific author wrote to Thatcher’s personal assistant Amanda Ponsonby, enclosing more supplements for the prime minister before her trip to the far east.

“I hope that there are enough because it is a very long trip,” Cartland wrote. “I did it myself and it does feel ghastly when you get home. Do impress on her that as far as I know there are no side-effects at all and they are not soporophic [sic], so that you feel you must go to sleep. It just stops that awful feeling in the head and ears.”

Earlier in 1989, Thatcher was visited at home by Emmanuel Kaye, an industrialist who also dabbled in alternative health. He had previously written to the prime minister about his “medical activity … an advanced form of homoeopathy called body tuning”. He claimed to have helped close friends and family with this method. Whether he “body tuned” the prime minister is unknown.

The public was given some insight into one of Thatcher’s dubious health remedies in a profile published in Vanity Fair in 1989. The article detailed her use of “electric baths” to stay youthful. It said she visited an Indian practitioner who would run 0.3 amps of electricity through water.

The profile may have contributed to a perception of the Iron Lady as “slightly off her trolley”, a description attributed to a Tory backbencher that was put to the prime minister, to her chagrin, in a television interview with Brian Walden in October of that year.

The papers can be viewed from Monday at Cambridge University’s Churchill Archives Centre and hundreds will go online at www.margaretthatcher.org.