Duchess Sophie and Prince Edward share the adorable secret to their happy 25-year marriage

Duchess Sophie and Prince Edward shared the heart-warming secret to their happy 25 year marriage during their joint visit to Nepal.

Almost twenty six years after they tied the knot at Windsor Castle, the Duke and Duchess of Edinburgh are one of the most iconic British royal couples. They’re not afraid to sing each other's praises at engagements and now they’ve made a special revelation during their six-day visit to Nepal this month. Throughout their trip Duchess Sophie and Prince Edward visited many vital organisations including the Ridley Eye Foundation, Maiti Nepal and Gurkha Welfare Trust’s Area Welfare Centre and championed causes close to their hearts, from maternal care to the Duke of Edinburgh’s International Award.

However, it was unsurprising that they also shared a few personal insights too and according to Hello!, they were asked by the media about the secret to their 25 year marriage. Prince Edward apparently declared, "Because we’re best friends" and Duchess Sophie added, "that’s true".

This couldn’t have been a more simple - or heartfelt - response from the Edinburghs, who married in June 1999. Friendship as well as romance are something they feel is key to the success of their marriage and they looked delighted to be in each other’s company during their time in Nepal. This trip had a particularly packed schedule and Duchess Sophie explained the non-negotiable that she and Prince Edward have, which becomes all the more important when they’re travelling.

"There's always got to be humour. Especially when you're travelling, and you’ve got no idea what's about to happen. You've got to laugh," she shared, adding that there’s also "always" got to be a sense of good-natured competition - "Got to be competitive going up those hills."

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The couple got stuck in with some planting as they toured the National Botanic Garden on Day 3 and Prince Edward described the "banter" that went on before this moment.

He explained, "There was a wonderful confusion because they wanted us both to plant the tree but then Sophie was then going to go and plant a rhododendron. We felt, 'Well, hang on a minute, if you're going to plant the rhododendron (the national flower of Nepal), I should plant the tree'. There was a lot of banter going on."

In the end Duchess Sophie did plant the rhododendron and she cheered her husband on as he planted the tree. Their sweet revelations about their relationship come a year after the Duchess described her husband as both her "best friend" and "guide" in a speech at the Community Sport and Recreation Awards before his 60th birthday.

She declared, "He has been my guide and shown me the way over the years. He has given me much help and advice (not always taken I admit), and his knowledge and instincts that have been honed over decades of service are invaluable - so we share speech notes (not this one, sorry darling!), chat through issues our patronages may be tackling, and together I think we make quite a good team."

"He is the best of fathers, the most loving of husbands and still is my best friend. So here's to you my darling Edward and may I along with all your family and so many friends and many others wish you the Happiest of Birthdays!" she concluded her speech.

In recent years we’ve seen many members of the Royal Family taking a more personal approach with messages and at engagements, and this moment reflects this in the most moving way.