The Queen is understood to have had a "soothing" friendship with a female member of the Royal Family who she felt closer to than any other - with the exception of daughter Princess Anne.

According to a royal biographer, it was the Duchess of Edinburgh who the Queen formed such a close relationship with that the pair would often spend time together watching old war films and documentaries.

Ingrid Seward told OK!: "With the exception of her daughter Anne, the Queen was closer to Sophie than any of the other royal women.

"It really was a genuine closeness, and Elizabeth was always Sophie's biggest confidante.

"The Queen found her very down to earth, because she refused to have expensive security and things like that, and she loved her lack of airs and graces.

"I think she saw Sophie as a bit of a surrogate daughter, too."

In a speech in 2019, Princess Sophie who is married to the Queen’s youngest son Prince Edward, referred to the monarch as "mama" suggest an almost maternal element to their fondness for one another.

The pair were often seen together at official events with Princess Sophie even invited to ride with the Queen to church services at Sandringham and Balmoral, with the monarch reportedly finding her company "soothing".

Following the Queen’s passing in September 2022, Sophie could be seen visibly weeping as she read cards and flowers that had been left by members of the public outside Balmoral.

She was also seen crying as her children, James and Louise, stood vigil by the Queen’s coffin in Westminster Abbey.

Royal writer and TV commentator Katie Nicholl said of the friendship: "Sophie had a wonderful relationship with the Queen, and she never saw it as a chore.

"She was very willing to step up and provide support when needed, and she did it with quiet enthusiasm, and always with a cheerful smile. I think in return, Elizabeth learned not just to rely on Sophie, but to trust her implicitly."

The two shared a love of military history and often raided the Windsor Castle archives.

Ingrid added: "They had a real love of military history in common. Sophie apparently once went to the First World War battlefields and museums of northern France, which obviously the Queen wasn’t able to do. So Sophie rang her from there to tell her about it."

According to reports, the pair were so close that Sophie even convinced the Queen to watch an episode of the Crown, although according to a courtier, "the Queen kept interrupting to point out when things were wrong".