Only they know the finer details, but for Kate Middleton and Prince William, it wasn’t love at first sight. She was dating someone else when they met as students at Scotland’s St Andrew’s University, but a year later caught his eye modelling in a charity fashion show.

And that was that. Kate and William later moved into a share flat, where she was wowed by homemade curries. After a brief split in 2007 – the story goes he dumped her by phone over pressure to marry – they wed and now share three kids, a love of skiing and reasonable real estate.

Kate Middleton and Prince William graduate from university. Photo: Twitter

Half an hour after Tasmanian Mary Donaldson first shook hands with a man introduced as “just Fred” at Sydney’s Slip Inn during the 2000 Sydney Olympics, she found out he was Prince Frederik of Denmark.

Drinks were had, jokes and numbers exchanged. After a long distance relationship, real estate agent Mary moved in with her man, who proposed in Rome and shed tears of joy during their cathedral wedding in 2004.

Now parents of four, Princess Mary and Prince Frederik – like Kate and William – are success stories when it comes to commoners marrying into royal dynasties and households.

But while the two women who will one day be queens are the pin up girls for mixing normality with institutions, their triumph in royal circles hasn’t been something other non-commoners have handled so easily.

Mary with Frederik and kids Josephine, Vincent, Christian and Isabella in 2018. Photo: Getty

In January, Meghan Markle called time on her stint as a senior royal, 18 months after marrying Prince Harry. The former actress knew when she pledged her troth to Harry she was also agreeing to life in harness as a working royal, but the gloss wore off quickly.

While the Sussexes’ marriage remains firmly intact amid their unprecedented retreat from life in the Windsor bosom, courtiers have whispered whether Britain would have had more luck holding onto their prince if he’d married an aristocrat who knew what to expect from royal life, not a Los Angeles starlet.

The same question arose on February 11, when news broke the Queen’s grandson, Peter Phillips, is getting divorced from his wife of 11 years, Canadian former management consultant Autumn Kelly.

As with Mary and Frederik, there was an instant spark when Peter – who called it “fate” – and Autumn met at the 2003 Montreal Grand Prix.

Peter and Autumn Phillips at Princess Eugenie’s 2018 wedding. Photo: Getty

They were soon playing house in Kensington, with the use of a cottage on the Gloucestershire estate of Peter’s mother, Princess Anne. A few years on, he proposed during a country walk.

“I looked horrible in my wellies with wet hair,” the bride told The Telegraph. “I said ‘Yes’ straight away, though.” They also said yes to selling their wedding photos to Hello! magazine, dividing royal ranks.

Peter and Autumn’s decision to throw in the towel reportedly “upset” the Queen, but that may be more down to timing as much as anything. At 93, the monarch is still dealing with fallout from Prince Andrew’s exile and negotiating a final ‘Megxit’ with Meghan and Harry.

Truth is, the royals are no stranger to divorce. The Queen’s late sister, Princess Margaret, was a divorcee, and three of her four children have failed marriages behind them, all involving commoner spouses.

Prince Charles’ union with Lady Diana Spencer – who, as a blue-blood aristocrat, was felt before her 1981 marriage to understand what she was in for – famously fell apart after 11 years.

The royal family reportedly had high hopes for Prince Andrew’s boisterous commoner bride, Sarah Ferguson, but factors, including his time in the navy, and her submitting her toes to be sucked by her financial advisor John Bryan put paid to things.

Princess Anne’s marriage to Captain Mark Phillips ended after 19 years – which left children Peter and Zara Phillips statistically more likely to divorce themselves – making Prince Edward and his wife, the Countess of Wessex, as the last couple standing.

The newlywed Wessexes are waved off from their 1999 wedding. Photo: Getty

Before her 1999 wedding to Edward, Sophie Rhys-Jones ran her own PR firm. Her background is as middle class as Kate Middleton’s, and she has become one of family’s front-line workhorses.

Less successful: The Monaco royals, especially princesses Caroline and Stephanie. Lady Davina Windsor split in 2018 with her New Zealand carpenter husband after 14 years. T

Tragically, Princess Martha Louise of Norway divorced Norwegian playwright Ari Behn two years ago, only for him to take his own life last Christmas.

So, is one problem that the commoners aren’t hard-wired for the selflessness and duty required? Prince Harry said of Meghan’s desire to ditch that, “There was really no other option.”

Or is it just that the royals, with their traditions and protocols and expectations, scare off those not born to it?