King Charles III has officially been crowned at Westminster Abbey in a remarkable Coronation ceremony alongside his wife Queen Camilla.
A string of senior royals showed their support to the new King and Queen throughout the procession, with Princess Anne having a pivotal role in the ceremony as the "Gold Stick in Waiting".
But despite showing support for her brother Charles and Queen Camilla, one royal biographer says that The Princess Royal once gave Camilla the 'cold shoulder' when they first met.
According to a royal book released last year, Princess Anne issued a brutally honest prediction of Camilla's future as Queen.
Royal biographer Angela Levin revealed details of the royal's tumultuous relationship with Camilla in her biography 'Camilla, Duchess of Cornwall: A Royal Survivor'.
She claims that Queen Camilla initially found Anne's demeanour 'frosty' and 'difficult'.
In an extract of the biography, Levin said: "Like many people who didn't know Anne well, Camilla found her frosty demeanour difficult and somewhat unnerving to cope with [at first]."
In a shocking blow, Levin claims that 'Anne was, for many years, opposed to the idea of Camilla being granted the title of Queen Consort'.
According to the book, the Princess Royal even once claimed that 'Camilla will never be a true Queen'.
Princess Anne allegedly 'kept away' from Queen Camilla 'as much as possible' for years. The biography also details her rocky road to becoming accepted within the royal circle.
Levin said: "Princess Anne reportedly initially gave Camilla the cold shoulder. It was little consolation that the Princess Royal had also had a frosty relationship with Diana, for whom she had no time before she married Charles, and with Sarah, Duchess of York".
Commenting on the royal pair's past relationship, the expert continued: "Her relationship with Camilla was particularly awkward as they had both been involved with Andrew Parker Bowles".
Andrew Parker Bowles is the former husband of Queen Camilla, but Princess Anne was also previously romantically connected with Bowles since they dated in the Seventies.
Camilla's divorce from Bowles was finalised in 1995 after they had been living separately for years. She has two children with her ex-husband, Tom Parker Bowles, and Laura Lopes.
In her biography of the now-Queen Camilla, Levin writes: "For years the Princess Royal kept away from Camilla as much as possible. However, time has proven to be a healer and Anne has seen for herself how hard Camilla has worked for the monarchy and her sense of duty. Gradually, she became more amenable".
It appears that old wounds resurfaced ahead of the Coronation, as Princess Anne allegedly confronted Camilla over her new Queen title at a tense Coronation dinner with other members of the royal family.
The Princess Royal supposedly told her sister-in-law that her title is Queen Consort and not Queen, according to Princess Diana's dressmaker, David Emanuel.
He claimed that the topic of Camilla's new title is 'highly charged' and that a lot of people' are 'unhappy' and that she will be referred to as Queen rather than Queen Consort.