The hidden message in Diana’s gym gear

It looks like a normal picture of Princess Diana heading to the gym — but there’s a secret hidden in her outfit that displays her true genius.

At $300-a-month, a membership at the exclusive Chelsea Harbour Club gym is something of a bargain.

Not only will you be able to work out in one of London’s most exclusive gyms, but there is a very good chance that many mornings — just after school drop-off — you will be able to spy the future king of England getting his sweat on.

Not only is the Harbour Club Prince William’s workout destination of choice, it was his mother’s.

In the ’90s, Diana, Princess of Wales, made the fitness club (that’s what they were called in the ’90s) world famous.

And intriguingly, it was also where she executed one of her most cunning and brilliant media masterstrokes.

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Prince William and Diana enter Chelsea's Harbour Club in London in 1996. Picture: AP

It was a time when the Princess’ every move was dogged by the paparazzi. From her hairdresser’s to her favourite restaurants to, yes, her beloved gym. Day in and day out, the royal’s haunts were the hunting ground for the voracious press pack.

Only a few years earlier, in 1993, she had sued the owner of another West London gym after he sold photos of her working out inside the gym to European, British and American tabloids.

Every day, they would stake out the Harbour Club, using stepladders to get better angles and shots. And every time she went there, she would scurry inside. You can watch YouTube videos of it. She looks hunted and deeply uncomfortable.

But the 30-something had a plan to strike back.

Princess Diana rocked the same sweatshirt — again and again and again. Picture: Anwar Hussein/Getty Images

At some stage, Virgin impresario Richard Branson had given Diana a branded sweatshirt bearing the company’s iconic logo. For all intents and purposes, it probably should have just ended up in the back of her cupboard beside forgotten T-shirts and discarded ’80s puffball dresses. Instead, she deployed it to devastating advantage.

The Princess decided that every day she would wear the jumper to enter and leave the Harbour Club. By donning the very same dull piece of clothing every time she arrived for a workout, Diana was ensuring the baying paparazzi got essentially the same shot of her.

Day after day, week after week, thus denying them any new (and saleable) shots of her.

It was a truly deft move that was slyly powerful. At a time when the newly separated HRH was struggling to find her voice, it was a truly brilliant “f**k you” to the press that often made her life hell.

Diana’s sweatshirt is now up for grabs, set to fetch upward of $61,400. Picture: Anwar Hussein/WireImage

This particular piece of royal history is now for sale. Diana later gifted the (very sweaty, we’re guessing) sweatshirt to her longtime personal trainer Jenni Rivvett. If you are eager to snap up this truly unique memento, you better have deep pockets. At the time of writing, the highest bid is $61,471.

“It became her most worn top on her regular visits to the gym,” Ms Rivett writes in a letter that accompanies the sale. “She felt there were far more important issues to focus on in the world then her gym attire and therefore decided that wearing the famous Virgin sweatshirt to every session would be a good way to stop the media frenzy!”

Sadly, Diana’s media-destroying tactic only kinda worked. Despite snappers being denied any particularly new or exciting shots of the mum-of-two, they would still set up and wait for her outside the Harbour Club.

It’s interesting to contrast that frenzy that greeted her every time she felt like working up a sweat with the reality her son faces.

There has never been a pap shot of him arriving or leaving from the Harbour Club. So much has changed in 20-odd years, and luckily, he doesn’t need any stealthy sweatshirt antics.

Now the only thing he has to worry about is forestalling the dreaded middle-aged spread. Godspeed Your Highness.

Daniela Elser is a royal expert and freelance writer with 20 years’ experience who has written for some of Australia’s best print and digital media brands. Continue the conversation @DanielaElser