Britain's Prince William "regularly" asks Queen Elizabeth II for her "secret" to having a long and successful marriage.

Duke and Duchess of Cambridge and Queen Elizabeth II

Duke and Duchess of Cambridge and Queen Elizabeth II

The 33-year-old prince - who is married to Duchess Catherine, 34 - often turns to his grandmother to seek advice on how to achieve a long and happy marriage like the one she shares with his grandfather Prince Philip, Duke of Edinburgh.

Speaking during a BBC documentary to mark the monarch's 90th birthday, titled 'Elizabeth at 90 - A Family Tribute' which aired on Thursday (21.04.16), the handsome royal said he is in awe of his grandparents, who are the "most lovely couple", and shared: "I would love to know their secret, it's actually fantastic and I have regularly asked them both how on earth they have both managed it. They are the most lovely couple, and I hope Catherine and I have that sort of future ahead of us, where we can be as happily married as they are for 68 years."

But William - who has two children, Prince George of Cambridge, two, and 11-month-old daughter Princess Charlotte of Cambridge, with Catherine - thinks one of their secrets to a happy life is always keeping their family close by.

He added: "I think she loves having her big family around her and knowing where they are and making sure they are OK. And it's a very kind of subtle attention that she has. So she keeps an eye and you don't necessarily know it, but she she knows exactly what you're up to and what's going on."