She was a genuine queen living just a few hundred yards from Buckingham Palace – yet she was NOT a welcome guest. Can you guess why?

She was a queen who lived only a few hundred yards from Buckingham Palace, but was not a welcome guest.

Once she wore tiaras and mingled freely with the crowned heads of Europe – but now not even a Christmas card!

So what was it about Queen Mary of Yugoslavia – a cousin of both Queen Elizabeth II and Prince Philip – that earned her the royal cold shoulder?

Was it her overbearing manner – Lilibet’s uncle described her as ‘That bitch’?

Queen Maria of Yugoslavia, consort of King Alexander of Yugoslavia in a 1922 portrait

Queen Maria of Yugoslavia, consort of King Alexander of Yugoslavia in a 1922 portrait

Alexander of Yugoslavia, and Princess Maria, who would soon become his bride

Alexander of Yugoslavia, and Princess Maria, who would soon become his bride

Queen Maria of Yugoslavia attends the unveiling of a sculpture on Armistice Day in Belgrade, created as a tribute to France by sculptor Ivan Rostrovitsch

Queen Maria of Yugoslavia attends the unveiling of a sculpture on Armistice Day in Belgrade, created as a tribute to France by sculptor Ivan Rostrovitsch

Was it that she was a swindler and manipulator, intent on usurping the rule of her son, the young King Peter?

Was the reason Maria cut such an unremarkable figure in public that she could easily be mistaken for a cleaning lady?

Or was it – in an era when such things really mattered among the royal families of the world – that she was a lesbian living openly with her lover?

History will probably decide that it was a combination of all these things. But at the top of the list, without a doubt, was her sex life.

Maria was born the daughter of a king and the great-granddaughter of Queen Victoria. Her brother was a king, her sister a queen, and she married King Alexander I of Yugoslavia.

Her credentials could not be more impeccable.

But it was a schoolgirl crush at the famous Heathfield school – whose more recent pupils have included Princess Alexandra and Prince William’s former nanny Tiggy Legge-Bourke – that signaled her preferred course in life.

Maria, daughter of King Ferdinand I of Romania, arrived at the school in the summer term of 1919.

She spent her teenage years nursing the wounded in her native Yugoslavia during the First World War. By the time she arrived at Heathfield – described by her parents as a ‘finishing school’ but actually a secondary school for the upper classes – she was, unusually, 19 years old – but as one of the royals best connected in Europe, the doors were opened wide to receive her.

Chubby but beautiful Maria – known as ‘Mignon’ – was placed in Form Va, where she sat next to Rosemary Cresswell, illegitimate daughter of a wealthy guard officer, Addison Baker-Cresswell.

The important thing was that Rosemary was four years younger than Maria.

The princess’s mother hoped that a dose of English public schooling would ‘help her slim down and keep her in touch with royal potential’” – in other words, future husband prospects. But she only had eyes for Rosemary.

On his return for the autumn term, Maria – now approaching her 20th birthday – was placed in the sixth form, while Rosemary, just 16, remained in the fifth. In the spring term of 1920, they continued their studies – but suddenly, and without explanation, both girls left school at the same time.

If there was a scandal, it was hushed up. Historian Ricardo Sainz de Medrano describes their relationship as ‘lesbian’ – but whatever the nature of their relationship while at Heathfield, in Form Va they forged a lifelong bond.

When they left, Maria was ordered to return to the Balkans to pursue her royal destiny. Soon she agreed to marry King Alexander of Yugoslavia – a piece of dynastic matchmaking that suited all parties except Maria.

Nevertheless, she bore the king three sons – Peter, Tomislav and Andrew – before His Majesty was assassinated by a Macedonian gunman in 1934.

Two years later, freed from the shackles of marriage, Maria left the country forever to live in London with Rosemary, who during their time apart tried married life with an English soldier, Archie Probart Jones, but found it just not her

The couple made their home in a flat near Chelsea’s Sloane Square, and although they were now forced to live modestly, the Queen never forgot her status, insisting that Rosemary be her ‘Lady-in-Waiting’ ‘ must be known.

This helped explain the couple’s closeness.

A mile away, Mary was viewed with disfavor by the royals at Buckingham Palace, who found her both intrusive and a nuisance. Her son may have become Yugoslavia’s king at the age of 11, but Maria disliked him and instead favored her other two sons. She deliberately cut Peter off and at the end of the war the boy king was deposed in a communist takeover.

Queen Elizabeth, later the Queen Mother, meets Queen Maria of Yugoslavia, widow of King Alexander I of Yugoslavia

Queen Elizabeth, later the Queen Mother, meets Queen Maria of Yugoslavia, widow of King Alexander I of Yugoslavia

King George VI entertains members of the royal families and the heads of the allied governments who are now in London at Buckingham Palace

King George VI entertains members of the royal families and the heads of the allied governments who are now in London at Buckingham Palace

Queen Maria, mother of King Peter of Yugoslavia, at her English country home with her two younger sons, Prince Andrej (left) and Prince Tomislav

Queen Maria, mother of King Peter of Yugoslavia, at her English country home with her two younger sons, Prince Andrej (left) and Prince Tomislav

King George VI, Peter’s godfather, deplored Mary’s determination to interfere in her son’s rule. His brother, the Duke of Kent, dubbed her ‘The Fat One’ and added for good measure, ‘she really is a bitch.’

Marie and Rosemary, friends with the romantic novelist Barbara Cartland, moved to a house near Cambridge during the war, where Rosemary effectively became the two boys’ mother while the Queen sat in bed chain-smoking cigarettes. The queen grew in size and impurity.

King Peter and his mother would never make contact again. She died in 1961 and – despite the lack of invitations from Buckingham Palace – was given a place in the royal cemetery at Frogmore, Windsor, before being reburied in Serbia in 2013.

As for Rosemary, there was no such grand farewell. She died anonymously in 1983, taking the many secrets of her unique 37-year relationship with a queen to the grave.