Princess Margaret described the Queen as having a ‘kind of magic’

Author Andrew Duncan has written in the Radio Times of how Margaret talked of trying to help her older sibling with her “burden” of royal duty, but that it could be “very formal and boring”.

“My sister has an aura,” the princess said. “I’m enormously impressed when she walks into a room. It’s a kind of magic.”

Margaret, who was interviewed by Duncan in the late 1960s, added: “In my own humble way I’ve always tried to take some of the burden off my sister.

“She can’t do it all … and I leap at the opportunity to help.

“Sometimes it can be very formal and boring, but I’ve got a reflex against that now. It’s very much up to one not to be bored.”

Neflix’s The Crown series has rekindled interest in the princess, who was known for her glamorous lifestyle and turbulent love life.

In the 1950s, she fell in love with the divorced Group Captain Peter Townsend – but renounced him after coming under political, family and church pressure.

She wed and later divorced photographer Antony Armstrong-Jones, who became Lord Snowdon, and went on to have an affair for several years with Roddy Llewellyn, who was 17 years younger.

Margaret, who died in the Queen’s Golden Jubilee year of 2002 at the age of 71, suggested that the success of the monarchy depended on the royals producing “nicely brought up young people”.

Duncan told how the princess, who was just 39 at the time, said she had mellowed with age and was less inclined to subject people to withering looks.

“My friends used to tease me and call it my ‘acid-drop’ expression….I’m much nicer in old age,” Margaret said.

This week’s Radio Times is on sale from September 4.