King and Queen Camilla joined by Peter Phillips and his fiancée at Balmoral in special moment for couple

The Princess Royal, Sir Tim Laurence, Prince Edward and the Duchess of Edinburgh have also all spent time at Balmoral this summer.

Harriet Sperling’s appearance at Balmoral alongside other royals is the first time she has joined senior family members for the summer break.

She was unable to travel to Scotland last year amid work commitments in her role as an NHS pediatric nurse.

Balmoral is one of the few times each year when the extended Royal Family gathers away from official duties.

A source told the Sun: "Everyone knows Peter is smitten and his family have accepted Harriet into the set up so she will likely pass the infamous Balmoral Test with flying colours."

It comes just weeks after the couple confirmed their engagement with an official statement.

Princess Anne’s son announced his engagement to Harriet Sperling on August 1.

The statement read: "Mr Peter Phillips, the son of HRH The Princess Royal and Captain Mark Phillips and Ms Harriet Sperling, daughter of the late Mr Rupert Sanders and Mrs Mary Sanders of Gloucestershire, have today confirmed their official engagement.

"Both families were informed jointly of the announcement and were delighted with the wonderful news of their engagement.

Their Majesties The King and Queen, The Prince and Princess of Wales have been informed of the announcement.”

The statement added that “no date has been officially set for the wedding”.

Last month, Peter Phillips and Harriet Sperling attended the tenth day of Wimbledon.

The couple were pictured watching the quarter-final matches at the All England Lawn Tennis and Croquet Club.

However, they were not sitting next to Queen Camilla, who also attended the prestigious sporting event on the same day.