The sweet, sisterly gesture that shows Sophie Wessex has become Kate's 'wing woman' - and, as REBECCA ENGLISH reveals, a source of strength during cancer treatment

It  was the sweet, spontaneous gesture of sisterhood that told us more about the future of the Royal Family than any public pronouncement ever could. Leaving the Remembrance Sunday ceremony last weekend, the Duchess of Edinburgh placed a gentle hand on the Princess of Wales’s back and – in doing so – publicly cemented her role as Catherine’s ‘wing woman’.

Whether giggling in a landau at Royal Ascot or swapping amused glances over their husbands’ plumed finery at the Order of the Garter procession, the two HRHs have fast become a royal double act.

While it would be easy to liken their relationship to the giddy days of Diana and Fergie’s royal friendship, steady Sophie and careful Catherine are a very different proposition.

At first glance their closeness is surprising: the 59-year-old duchess broke boundaries before her marriage to Prince Edward, setting up her own PR business and becoming the first royal girlfriend to stay over at the Palace.

Despite being 17 years younger than her ‘aunt-in-law’, Catherine has never been one to rock the boat. She took a part-time job (with fashion brand Jigsaw) after university that fitted round her relationship with the heir to the throne.

The public causes they associate with as working royals also point to differences.

While the future Queen has focused on domestic issues such as mental health and the well-being of under-fives, Sophie has travelled solo to Chad, Ethiopia and even war-torn Ukraine – campaigning on women’s rights and the use of sexual violence as a weapon of war.

And yet there is no competition between them, as was sometimes claimed in the early days of Diana and Sarah.

Both respect each other’s work and they are mutually supportive of their approaches to their royal roles.

I am told Catherine also has ‘enormous admiration’ for Sophie as mother to Lady Louise Mountbatten-Windsor, 21, and the Earl of Wessex, 16 – both of whom have been brought up to value their privilege while having freedom away from the royal radar.

It’s an approach Catherine is trying to adopt with Prince George, Princess Charlotte and Prince Louis within constrictions of their higher profiles and future roles.

Catherine is said to be especially fond of level-headed Lady Louise, studying English literature at her alma mater St Andrews.

Louise is a member of the University Officers’ Training Corps and keen to pursue a career in the military, diplomacy or law. Some in royal circles suspect that, under a future King William V, Lady Louise could be called on to support the family at an increasing number of royal engagements – and shore up their dwindling ranks.

‘She’s an absolutely delightful young woman and would be a real asset,’ says a family friend.

Sources say that both the princess and the duchess’s comfortable, middle-class upbringings have also given them a unique approach to royal life.

While Catherine’s parents made their fortune from her mother Carole Middleton’s party goods business, Sophie’s father, now 93, was sales director for an importer of industrial tyres and rubber goods. Both enjoyed sporty, outdoorsy childhoods and have a passion for skiing and tennis.

And the strength of their own family relationships has prevented either from being ‘consumed’ by the institution.

While Sophie lost her mother Mary Rhys-Jones 19 years ago, her father Christopher remains a huge presence in her life.

Likewise the Middletons, who live close to the Waleses’ home in Berkshire, and continue to provide Catherine with a much-needed link to the ‘outside world’.

Their relationships have also enabled both royals to keep a healthy distance from internal family politics.

Interestingly, I am told, both ‘repeatedly’ reached out to Meghan when she joined the Royal Family – Sophie particularly so as the late Queen valued her wise and steady counsel.

They continued to do so even after the Duchess of Sussex first publicly voiced her unhappiness in 2019, telling journalist Tom Bradby that few people had asked if she was ‘OK’ as she struggled to adapt to royal life.

Both women were ‘shocked’ (and probably slightly angered) at the suggestion – not least because they felt it was Meghan who had rebuffed them.

But I know they were concerned enough at the apparent strength of the Duchess of Sussex’s feelings that they continued to offer their support. Needless to say, it was not taken up. There is no doubt the ensuing ‘Sussex saga’ brought Sophie and Catherine even closer as they defended Queen Elizabeth, their own families and the institution they had worked so hard to support.

That relationship has only been strengthened over the past, difficult year. It’s helpful the two women live 20 minutes drive from each other – Catherine at Windsor and Sophie at Bagshot Park.

And the duchess is perhaps uniquely placed to offer some personal understanding of Catherine’s health battle as it plays out in the public eye.

In 2001, Sophie suffered a life-threatening ectopic pregnancy after collapsing at home.

Two years after that loss, she was ‘minutes from dying’ when she delivered her first baby Lady Louise – losing colossal amounts of blood and requiring an emergency C-section. Her pregnancy with son James was also dangerously complex.

But it is on other lifestyle matters that they have bonded.

Both are keen countrywomen and ‘gym bunnies’ (everyone agrees Sophie is looking better than ever as she approaches her 60th birthday in January) and have shared fashion tips.

Designer Donna Ida revealed that Catherine so admired a £295 black jumpsuit the duchess had bought from her collection that she snapped up one as well.

‘Super’ Sophie also came to Catherine’s discreet rescue at Princess Eugenie’s wedding in 2018, rushing to pull down her dress as it was whipped up by a gust of wind. Talk about girl code!

It’s clear to see why the late Queen considered her daughter-in-law such a safe and reliable pair of hands.

It would have greatly pleased her, family friends say, that the duchess has become such a trusted confidante for her beloved grandson’s wife.

And those friends have no doubt that she will continue to be an increasing source of strength and counsel as Catherine approaches her future role as Queen.

‘There have been some really kind and wise people along the way who have helped the princess over the years, and Sophie is very much one of those,’ one royal insider says. Mark Foster-Brown, the Edinburghs’ close friend, has also echoed this, previously telling me: ‘Sophie has been a very positive reference point and sounding board for the Duchess of Cambridge. Their relationship has really strengthened. It will be absolutely critical for [the princess] to have a female backup.

‘And she simply couldn’t get better than someone like Sophie.’