Mrs Thatcher, who famously slept for only four hours a night, received “nutrimental capsules” from the novelist “in case you ever feel tired”.
On a separate occasion Mrs Thatcher was sent a further supplement, possibly to address jetlag or travel sickness ahead of a trip to the Far East. Dame Barbara, who corresponded with Mrs Thatcher fairly regularly and lunched with her, sent a package dated 8 June 1989.
“My dear Prime Minister,” she wrote. “You were wonderful last night, as usual.
“It is incredible, with all you do, how you can still look as though you were 25.
“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, and at nearly 88 I find it fantastic.”
In a letter dated 15 June 1989, Mrs Thatcher thanked Dame Barbara for the “charming letter” and the “nutrimental capsules”. Dame Barbara wrote to Mrs Thatcher’s diary secretary Amanda Ponsonby on 3 July 1989 with further supplements ahead of Mrs Thatcher’s planned trip to the Far East. “Thank you so much for being most kind and saying that you will give the enclosed to the Prime Minister,” wrote Dame Barbara.
“I hope that there are enough because it is a very long trip.
“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 soporific, so that you feel you must go to sleep.
“It just stops that awful feeling in the head and ears.”
Millionaire industrialist Sir Emmanuel Kaye, once a strong supporter of the Conservative Party, wrote to Mrs Thatcher after seeing her at the opera at Glyndebourne offering advice about her supplements. He said he could “sort out vitamins, minerals etc and, if you like ... check whether the Vitamin C and the Royal Jelly you are having are of the best variety for you and work out the optimum dosage”.
The Margaret Thatcher Foundation is gradually overseeing the release of her private files.