Kensington Palace preparing for Harry and Meghan's engagement

It is not just a new part for Meghan Markle, but a role to last a lifetime. For while many are preoccupied with last week's news of a third baby for the Cambridges, another announcement is being quietly prepared behind the gates of Kensington Palace.

Today The Mail on Sunday can reveal that officials are drawing up what they consider to be an inevitable announcement - of an engagement between Prince Harry and the American actress who has been by his side for more than a year.

The Suits star has met her prospective in-laws, the Prince of Wales and Duchess of Cornwall, and is said to have made a good impression. The couple's first official public appearance together is expected at the Invictus Games in Toronto later this month.

Significant changes are even afoot within the palace itself, changes which will open up the possibility of a new family home at Apartment 9 for Harry and Meghan.

They currently stay in Nottingham Cottage, a small two-bedroom house in the palace grounds.

It has become clear that Royal solicitors Harbottle & Lewis, which acts for Prince Charles, William and Harry, has been asked to represent Meghan, too.

And it is understood that Kensington Palace has been playing a key role in reducing the actress's publicity commitments to the TV legal drama Suits, an apparent clearing of the decks and part of what some are calling "Operation Princess".

Is this all a careful preparation for a new and much more regal way of life? Certainly, many believe the couple are "as good as engaged" following their romantic hideaway holiday in Botswana last month.

The Mail on Sunday has learned that they have stalled an official announcement, fearing it would overshadow the 20th anniversary of Princess Diana's death. Harry, along with his brother, has been a figurehead for a summer of national remembrance and celebration of his mother's legacy.

Now, however, with the key date past, he is free to confirm that Miss Markle will become his wife. This is expected to become clear at the Invictus Games on September 23, where the two will appear together for the first time at a public engagement.

The games, which feature injured and disabled Servicemen, are Prince Harry's passion project, and Toronto - the city where Suits is filmed - is Miss Markle's adopted home.

Sources say Kensington Palace are preparing for an engagement announcement. Photo / Getty Images

Afterwards it is thought she may spend more time in London with the Prince, a full-time working Royal. She is already a regular guest at his bachelor quarters and is on good terms with their neighbours, the Duke and Duchess of Cambridge.

Ms Markle's meeting with Charles and Camilla is felt to be particularly significant. "Harry's father is just keen for him to settle down and be happy," says a source.

"Both Charles and Camilla are understood to have held back from expressing views, keen that Harry should have his own space to make his own decision."

One palace insider said: "Harry was nervous of introducing Meghan to them because he did not want people to jump to conclusions about someone he deeply cared for. He wanted to consider in his own time whether or not she might have a permanent place in his life."

Meghan is already friends with Harry's cousin Princess Eugenie and has forged warm relationships with those closest to him, such as his "second father" Mark Dyer, a former equerry to Prince Charles, who has mentored Harry since childhood. That said, Royal protocol makes it unlikely that Meghan will meet the Queen until the official engagement announcement.

Meghan is thought by some senior courtiers to have already breached Royal etiquette with her recent Vanity Fair interview. Her appearance on the magazine's cover to promote the 100th episode of Suits had been sanctioned by Prince Harry and Kensington Palace, but is said to have been greeted with surprise and dismay by Buckingham Palace.

There was also a photoshoot in which she was pictured in a black-and-white taffeta evening dress, an intriguing echo of a famous Snowdon portrait of Diana barefoot in an evening down.

Miss Markle told Vanity Fair: "We're a couple. We're in love. I'm sure there will be a time when we have to come forward and present ourselves and have stories to tell, but I hope what people will understand is that this is our time.

"This is for us. It's part of what makes it so special, that it's just ours. But we're happy. Personally, I love a great love story."

The comparatively intimate nature of the comments, combined with the fact the interview was to advertise a TV show, is thought to have caused concern to senior Royals. But Miss Markle believed she had a professional responsibility to her television bosses and is set to give one further interview to a US publication. After that, Buckingham Palace is likely to want to take a degree of control over the actress's public life, not least because of her complex background.

Prince Harry is currently fifth in line to the throne. Photo / Getty Images

Meghan is three years older than Harry, a divorcee and of mixed race, with a mother who is black and a father who is white. Her nationality and the fact that she is a divorcee also raises the spectre of Wallace Simpson, whose relationship with Edward VIII led him to abdicate, causing a constitutional crisis in 1936.

Prince Harry is fifth in line to the throne and will become sixth after the arrival of the Duke and Duchess's third child.

Marriage to Miss Markle would have no constitutional ramifications but the palace would wish to protect the public profile of a woman likely to become a full-time working Royal, and perhaps mother to a new generation of Royal children.

Not that it will be easy. There is every prospect that both the Prince and senior courtiers must resign themselves to a future in which unexpected and unwelcome revelations emerge from the US.

None of this is deterring the young couple, of course.

Plans were last week approved for a vast basement beneath Kensington Palace's Grade I-listed Orangery. The huge renovation will provide more than 1,500 square metres of office and storage space over three floors - two below ground and one above.

Although the Historic Royal Palaces insists that members of the Royal Family have no involvement in the project, the planning application submitted to Kensington and Chelsea Council suggests otherwise, stating that: "The addition of a basement storey is required to allow for the accommodation of administration which must necessarily be moved out of rooms leased from the Royal Household in Kensington Palace."

News of an engagement would be welcomed on both sides of the Atlantic. Prince Harry is one of the most popular Royals and Meghan has been praised for her humanitarian work and charity work.

It is true that she already lives in the public eye and is comfortable with her existing celebrity status, but is her judgment good enough to distinguish between acting in the interests of the Royal Family rather than to her own advantage?

Miss Markle and the Prince met in June 2016 over drinks at Soho House, a London private members' club. They managed to keep their romance secret for six months but have since been pictured going out privately in London, heading off on holiday, and attending a Caribbean wedding and a polo match together.

Born in Los Angeles, Meghan married film producer Trevor Engelson after seven years together, but the couple split two years later.

Now, with engagement seemingly imminent, she may have passed her biggest audition of all.

Divorced star won't marry at Abbey

As a divorcee (she split from her first husband in 2013) and a Catholic, it is unlikely that Meghan would marry Harry in Westminster Abbey, which William and Kate used in 2011.
Nor are they likely to follow in the footsteps of the Prince and Princess of Wales, who married at St Paul's Cathedral in 1981.

Instead, they will probably consider St George's Chapel in the precincts of Windsor Castle, where the Earl and Countess of Wessex wed in 1999, and where the marriage of Prince Charles and the Duchess of Cornwall was blessed in 2005.

The couple might look north of the border to Canongate Kirk in Edinburgh, enabling them to host their reception at the Palace of Holyroodhouse like Princess Anne's daughter Zara did for her 2011 wedding to Mike Tindall.

Other possible venues include Crathie Kirk near Balmoral, venue for the 1992 second marriage of the Princess Royal to Vice Admiral Tim Laurence, or St Mary Magdalene in Sandringham, Norfolk.