Key reason Prince Edward and Duchess Sophie’s relationship is successful

is not only the late Queen’s youngest son, but he is also the only one of Queen Elizabeth II’s children to not have divorced.

Since marrying Duchess Sophie, 60, in 1999, the royal couple seem to have gone from strength to strength, with one royal expert now revealing how they have maintained the good relationship all this time.

The insight comes after the Duke and Duchess of Edinburgh, who have two children together, where the duke, 60, revealed that Sophie was his “best friend”.

Former royal correspondent Jennie Bond said this forms a central part of their marriage, with the couple being a great team and support for one another.

: “I think the strength of their marriage is rooted in a deep and lasting friendship, along with a healthy dollop of mutual attraction and true love.”

She continued: “She (Sophie) still finds Edward quite dashing and I’m sure he would agree that Sophie is as beautiful today as she was when they married. I think he is immensely proud of his wife.

“Sophie has been unusually open about her love for him. She said he was the most loving of husbands and that they were still best friends – and that’s something they both repeated on their recent visit to Nepal.

“Sophie said, quite rightly, that they make a great team. They are companions both on and off duty.

“They share notes about their work and talk through their speeches. Sophie has joked about how Edward gives her valuable support and advice, though she admits that she doesn’t always take it. That’s definitely a sign of a balanced, equal and supportive relationship.”

The couple are set to celebrate their 26th wedding anniversary this year.

Since their 1999 Windsor wedding, they , where Sophie once said they live a fairly ordinary life consisting of gatherings with friends, dog walks and spending time with their two children Lady Louise Windsor, 21, and James, Earl of Wessex, 17.