She may have been the no-nonsense grocer’s daughter who became the steely Iron Lady of No 10, but newly released papers throw a fascinating light on Margaret Thatcher’s interest in alternative medicines and bizarre therapies.

A series of letters between the Prime Minister and the romantic novelist Barbara Cartland appears to suggest that Mrs Thatcher flirted with treatments not necessarily prescribed by her doctors.

Miss Cartland appears to have regularly sent Mrs Thatcher supplements and ‘pep pills’ she felt would have a beneficial effect on the PM.

On June 8 that year Miss Cartland wrote to Mrs Thatcher enclosing “the very latest product we have in the Health Movement”.

The writer went on to wax lyrical about the effects of this product, which she said “takes oxygen to every part of the body, including the brain”.