See Princess Anne's priceless reaction to spotting Lady Louise Windsor

It's always a pleasant surprise to unexpectedly run into somebody you know, and that delighted feeling even occurs to the royal family.

Princess Anne proved that even she isn't immune to the joy of an unexpected rendezvous when she spotted Lady Louise Windsor during the Royal Edinburgh Military Tattoo in August.

In a series of candid photos, snapped by a fellow guest of the special event, Princess Anne can be seen beaming widely at her young niece, who returns the Princess Royal's wide smile.

Both Princess Anne and Lady Louise look overjoyed to see one another, with Prince Edward's daughter dressed in full military attire.

The Scottish event was one of the first the Princess Royal attended following her concussion, so it was likely the first time Lady Louise had seen her aunt for a while, hence the delight they both felt.

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Royal watchers loved the behind-the-scenes photo, commenting how proud Princess Anne looked of her youngest niece, who is following in her military footsteps. "Look at the smiles," one fan commented. "I think Lady Louise was a surprise to Princess Anne, but a lovely welcome surprise"

Lady Louise's military plans

Prince Edward and Duchess Sophie's daughter is clearly committed to her military pursuits, proven by the fact she is set to make history as the first female royal to serve in the military since the late Queen Elizabeth II.

The young royal, 20, is a member of St Andrews' University Officers' Training Corps (UOTC), which provides paid military training for students and while other female royals, such as Princess Anne and the Princess of Wales, hold military titles, these are honorary - neither have served in the military.

On the other hand, Her Late Majesty joined the Auxiliary Territorial Service (ATS) in 1945, becoming the first female member of the Royal Family to join the Armed Services as a full-time active member.

LOOK: The late Queen's sweetest moments as mother, grandmother and great-grandmother

Lady Louise, who is 16th in line to the throne, proved her commitment to her plan via her LinkedIn page, writing: "I am interested in pursuing a career in the military, diplomacy, or law."

Though she is set to follow in her beloved grandmother's footsteps, she takes after Princess Anne in many ways too. As an elder sister with a deep a love for horses, and a strong sense of duty, Lady Louise is similar to her aunt, Princess Anne, 74, who is known as the hardest-working royal.

We can't wait to see how the next few years pan out for Lady Louise.