REBECCA ENGLISH: As the Royal cousins touchingly support William, why Harry and Meghan are the reason they'll now never have a chance of a bigger role

So much has been said about family disunity in recent years that it’s sometimes easy to forget how well our senior royals get on with each other. They are remarkably close, in fact.

Standing side-by-side at a Buckingham Palace garden party yesterday, Prince William and his cousins added a welcome pop of youthful glamour not seen in the institution for a little while.

How touching that the future king – knowing he would be without his wife at his side – could call on Zara, Peter, Beatrice and Eugenie for support.

Encouragingly, I’ve been told by multiple sources that the Princess of Wales herself has been seen out and about more in recent weeks, although Kensington Palace has made it clear that Kate will not be returning to work until she has had the ‘green light’ from doctors.

Prince William hosted the first royal garden party of the year at Buckingham Palace yesterday

He was flanked by the Duke and Duchess of Gloucester, the only other working royals present

 After all, she has been through major abdominal surgery and then, later, a course of ‘preventative chemotherapy’ when the presence of cancer was detected.

This is why William personally invited close relatives, the nearest and dearest, accompany him as he stood in for his father yesterday.

Every member of ‘Team Wales’ was clearly delighted to attend – proud to support not only William, but also their uncle, the King, who was himself taking a short break from a busy week of public duties as he continues his own cancer treatment.

The presence of the younger royals gave Tuesday’s event a unique family vibe, as well as an insight into the easy relationship that William enjoys with his cousins. It’s a warmth that goes all the way back to fun family summers at Balmoral, Christmases at Sandringham – and now finds expression in the very modern medium of shared family WhatsApp groups.

It was 4pm when the royal party came out on to the Terrace overlooking the Palace lawn via The Carnarvon Room.

Resplendent in a morning suit and top hat, William was flanked by the ever-loyal Duke and Duchess of Gloucester, the only two other working royals present (and a couple so sweet that you often see them holding hands on royal engagements).

The King's niece Zara Tindall paired a Laura Green tea dress with a £900 Sarah Cant straw hat

Princess Beatrice and her sister, Princess Eugenie, spoke to the crowds and shook hands

William offered light banter about reading bedtime stories to his youngest son, Prince Louis

Following behind them was William’s posse of royal relatives: Peter Philips, 46, and his sister, Zara Tindall, 43 – son and daughter of the Princess Royal – led the way, along with Zara’s husband, Mike, the former England rugby captain.

Then came Prince Andrew’s daughters, Princess Beatrice, 35, and her sister, Princess Eugenie, 34.

It’s true that the continual rain was no respecter of royal protocol, yet the mood was joyful all the same as the guests enjoyed the absurd but fabulous Britishness of taking tea under umbrellas while not one, but two military bands played doggedly on.

William was charming, as he always is with the public. He posed for selfies and chatted, smiling, about everything from bedtime reading for his youngest son, Prince Louis, to his weakness for cookies. He took a bag of homemade treats from one well-wisher.

There’s no doubting his popularity – or that it’s growing. You could hear excited squeals and calls of ‘William, Prince William!’ as he walked past.

And, while the biggest draws such as the King and Kate weren’t present, the lesser-spotted members of the family caused a genuine frisson of excitement.

Professional equestrian Zara – looking like a sugar-spun Mary Poppins in a Laura Green ‘Isobel’ tea dress with an eye-catching £900 Sarah Cant pink straw boater – was easily the hit of the day.

She charmed the crowds with her throaty laugh and easy banter, happily ignoring the fact that her £495 pink suede Emmy London heels were turning to a dull rose in the rain.

Mike Tindall, a frequent speaker on the after-dinner circuit and a podcaster, was clearly another crowd pleaser and naturally comfortable with the crowds.

It was notable that Mike and Zara were asked to flank William as he moved along the lines to shake hands with, and greet, as many of his 8,000 guests as possible.

Sisters Beatrice and Eugenie, who are more occasional figures at summer events and large-scale Palace receptions, seemed happy to get stuck in, too.

I thought that Eugenie, who wore a white satin dress and 50s style headwear studded with flowers, bore a passing remembrance to Princess Margaret.

Beatrice, wearing a £750 crimson Beulah dress and checked headband, was never too far from her sister’s side.

It is true that the sovereign will often ask other family members to host garden parties. William hosted one such event last year.

But, given the current circumstance, Tuesday’s event throws up, intriguing questions about the future shape of the Royal Family – and the much-needed vitality that the younger generation brings.

Zara was joined by her husband, former England rugby captain husband, Mike Tindall, far left

William stood in for King Charles at the event, who continues to undergo treatment for cancer

Many royal-watchers have asked – and repeatedly: why can’t the cousins step in on a more permanent basis?

For Peter and Zara, this has never been an option. From the moment their mother, Princess Anne, chose not to accept titles for them, the Phillips children were always destined to grow up away from the main royal spotlight, perhaps fortunately so.

It is perfectly plausible that Charles, or more likely William when he becomes king, could call on their services more often. But they will never become full-time working royals while they have their own careers and young children.

The same applies to Princesses Beatrice and Eugenie, who also have young families and jobs, although their father, Prince Andrew, has never made any secret of his desire to see them have prominent royal roles.

Bea works for US-based tech company Afiniti, while ‘Eug’, as she is known to her family and friends, is a director at art gallery Hauser & Wirth.

All four support their own charitable endeavours privately.

The unfortunate truth, however, is that none of them will be asked to support the working royals on a more permanent basis, however badly they are needed. And for that they must thank the Duke and Duchess of Sussex.

Eugenie, who wore a white satin dress and 50s style headwear, while Beatrice sported a £750 crimson Beulah dress and checked headband

Those in the know tell me there is deep concern at Buckingham Palace that changing direction in this way would play into Harry and Meghan’s hands.

The Sussexes had been told very firmly by the late Queen Elizabeth that their preferred option of being ‘half-in, half-out’ royals while pursuing lucrative commercial careers was simply unacceptable.

This ruling was partly down to the Queen’s personal sense of service. But it also owed something to her quiet belief that Harry and Meghan’s allegiance to the almighty Dollar might supersede anything they promised to Queen and Country.

At the height of the ‘Megxit’ controversy, as it became clear Harry and Meghan would relocate to North America, I was told that Her Majesty was riled by the couple’s insistence they would continue to ‘collaborate’ with her in the future.

‘No-one collaborates with the Queen. This is not one of those ‘Kate Moss X Top Shop’ tie-ups!’ raged one well-placed source at the time.

Seeking commercial deals while acting on behalf of, or representing, the British head of state would also have been a clear conflict of interest, and Her Majesty knew that all too well.

Harry and Meghan could never accept it, of course, and here is the consequence: there can be no relaxation of the rules for any of the younger royals. It is full time or nothing.

The occasional garden party aside, more substantial roles for William’s cousins are out of the question – for now, at least.