Princess Anne just gave five-year warning to the royal family

As Princess Anne is gearing up to turn 75 next week, she's reportedly issued a warning to the royal family about something she's set to start doing in five years time.

The sister of King Charles III will celebrate the milestone birthday on August 15th and the celebrations are already underway.

She kicked the festivities off last month and her choice of how to do so certainly lived up to her nickname of the hardest working royal.

Anne began her birthday celebrations not with a huge party or lots of publicity, but by hosting more than 100 of her favourite charities at Buckingham Palace.

According to the Telegraph, the late Queen Elizabeth II's only daughter spent more than two hours at the bash, shaking hands with as many of the 200-plus guests as she could and thanking them for their work.

Colonel John Boyd, the Princess’s private secretary, told the charity reps that there has been a 'significant amount of interest' in how the British royal will celebrate.

Princess Anne has reportedly issued a five-year warning to the rest of the royal family (Hoda Davaine / Getty Images)

Assuring them of her plans, he said: "It probably won’t come as a surprise, given HRH’s commitment to you all, that the way the Princess wants to celebrate this milestone is to replicate what she’s done on previous significant birthdays and hold this charities forum, to once again understand how she can help you, at a time when the third sector is facing unprecedented challenges and transformations.”

Anne carried out her first public engagement in 1969 aged 18 when she opened an educational and training centre in Shropshire, and a year later began her longest association with a charity, becoming president of Save the Children and later patron.

And now, The Sunday Times' royal correspondent Roya Nikkah has reportedly revealed exactly how Princess Anne plans to spend the upcoming years of her life.

As per Gloucestershire Live, she told the Royals with Roya and Kate podcast: "I was told that she’s told her team, 'I'm going to start winding down a little bit at 80 in five years' time, and then I want to step back completely at 90.'"

This means the royal family seemingly have just five more years to make the most of Anne's unwavering commitment, before she begins to slow things down.

Making a comparison between Anne and the late Prince Philip, the expert added: "I thought the timeline was interesting – that she's looking at her father, the late Duke of Edinburgh, Prince Philip, who stepped back from public life completely at 96."

Princess Anne is often referred to as the hardest working royal - and with good reason (Aaron Chown - WPA Pool/Getty Images)

But by the looks of her busy calendar at the moment, fans don't need to worry, as it looks like she has absolutely no plans of slowing down any time soon.

Just last week on July 30th, she met with performers for this year’s Royal Edinburgh Military Tattoo, including members of a Ukrainian naval band playing for the first time since the full-scale war began.

And on July 23rd, Princess Anne attended the opening of an accessible garden for patients at the Princess Royal Spinal Injuries Centre, at the Northern General Hospital in Sheffield.

Last month, the Princess Royal was gifted a very high honour to celebrate the milestone birthday, as her face was put onto an official UK coin for the first time ever by the Royal Mint.

The commemorative coin includes a depiction of Anne's official Coat of Arms and the design is framed with the inscription: "The Princess Royal - Celebrating 75 Years - Duty and Devotion.”

Speaking of the historic decision, Rebecca Morgan, Director of Commemorative Coin at The Royal Mint, said: "For the first time in British numismatic history, we are honoured to celebrate The Princess Royal on an official UK coin.

“Her Royal Highness's unwavering commitment to public service, charitable work, and support of His Majesty's Armed Forces over seven and a half decades makes her truly deserving of this tribute.

“The graceful design by Thomas Docherty perfectly captures both her dignified presence and extraordinary legacy while also celebrating The Princess Royal’s 75th birthday."