When news broke in September 2012 that a French magazine had published intimate holiday pictures of the then Duchess of Cambridge, I had never seen her husband, Prince William, so angry.

Jaw clenched, he could barely contain his fury as they stoically continued to undertake a day of engagements in Malaysia as part of a hugely high-profile foreign tour to mark his grandmother Queen Elizabeth's Diamond Jubilee.

His anger was completely understandable: the instinctive reaction of a man whose wife was violated by the paparazzi, a hurtful re-imagining of the harassment he believes his late mother endlessly endured.

By contrast, Kate was the picture of cool, calm and utterly unruffled elegance. I remember covering a reception at the British High Commissioner's residence in Kuala Lumpur hours after the publication hit newsstands and marvelling how she was able to smile, shake hands and make small talk, without the slightest quiver or indication that anything was amiss.

Later in the trip, William quietly explained the depth of his fury –- not only at the intrusion his wife had been subjected to, obviously, but the fact that he had been unable to protect her from it.

He had promised her parents when he asked for their daughter's hand in marriage two years earlier that he would always do his best to protect her – and felt (wrongly, in my opinion) that he had failed.

I'm reminded of this as the now Prince and Princess of Wales prepare to celebrate their 14th wedding anniversary in Scotland tomorrow, an event I am currently en route to cover for Mail readers.

The fact that they are doing so in a very public setting – with all eyes on their interactions and body language – is unusual for this intensely private couple.

Kate and William wave from the Buckingham Palace balcony after their wedding in 2011

Rebecca English says she had never seen William so angry as on his and Kate's tour of Malaysia after the topless pictures of her had appeared in a magazine

And it shows how far they have come together since those testing times in Malaysia and their continued strength as a family unit.

It's important to stress that they hadn't intended for their anniversary to become a public event.

But when the dates came up for this two-day visit to the remote Isles of Mull and Iona and staff realised there would be a clash, William and Kate apparently thought 'why not?'

Sources tell me it's impossible to exaggerate their love for Scotland: it has played a unique role in their relationship, given that they met and fell in love at the University of St Andrews, and return to the Highlands each year for family holidays at Balmoral. 'It's definitely one of their 'happy places',' one insider says.

So it's a particular delight, sources say, for them to use the occasion to shine a spotlight on resilient island communities, local industries and the need for tourism in the region.

Of course it has been a particularly brutal period for them as a couple given Kate's cancer diagnosis last year.

But the experience has, friends say, also given them a greater appreciation of what they have together, including an increased willingness to share more of their private family moments with people (as we have seen in the regular video updates on Kate's health journey of late).

'They are as happy as anyone has ever seen them,' a well-placed source tells me.

Kate enjoyed a warm relationship with Prince Philip and saw him as a source of support and inspiration

Their relationship is far more balanced than many will realise, although the princess notably prefers to focus more on family matters and has taken her time in striking out on projects of her own, such as her Early Years initiative.

That's in part because she has always seen her role as a supportive one, much like the late Duke of Edinburgh was for the Queen.

A while back I revealed that the princess had been in frequent contact by letter with Philip for many years before he died in 2021, with the pair enjoying a 'warm and loving' relationship.

Kate, who had lost her own grandparents, saw Queen Elizabeth's husband as a source of support and inspiration.

'Philip was famous for writing letters in the family, but he was particularly thoughtful towards Catherine,' a family insider previously told me. 'He guided her to understand that royal service is what you make of it and was a valuable sounding board.'

That should not be to underestimate the princess's strength of character and strong personal will.

Above all, William is her equal partner in everything – not an 'i' is dotted or 't' crossed without their joint sign-off and collaboration.

'He flies off the handle at any sign of Catherine being patronised and stamps that out very quickly,' a friend once told me. 'It's one of his triggers. Over the years, many people have come up with great ideas for her, but if they are put across in a dismissive way, they've got pretty short shrift from him.'

There is, they say, a 'deep intimacy' between the couple, forged through their shared experiences in the public spotlight and William's admiration for Kate's abilities as a mother.

He particularly appreciates the way she has created a happiness and stability for their family that he didn't always experience growing up.

The smiling couple at the Commonwealth Day service of celebration at Westminster Abbey in March this year

All big decisions are taken together and their diaries approved only after the other one has agreed, ensuring that their children – Prince George, 11, Princess Charlotte, nine, and seven-year-old Prince Louis – are always put first.

They endeavour to ensure, where possible, that at least one of them will be available to do school drop-off or pick-up, and both are familiar figures at school sports pitches and dance recitals.

Their commitment to their family really does show when you see the happy little faces of the young Waleses in public.

The children aren't accompanying them to Scotland tomorrow – all three will be at school – but this will also happily afford William and Kate the chance for a quiet night away together on the Isle of Mull, where they have romantically booked an isolated self-catering cottage 'à deux' – and perhaps the chance to ruminate on what an incredible decade or so it has been, with even more extraordinary times to come.