The Duke of Sussex has organised a birthday getaway to the Californian mountains near his home with a few of his closest mates.

Prince Harry is gearing up for a hike on his 40th birthday (Image: Getty)

Prince Harry will mark his 40th birthday this Sunday with a private celebration in Montecito, surrounded by family and friends. However, he is also planning a rather unsual afterparty for himself and his pals.

Express.co.uk has learned that the Duke of Sussex has organised a getaway to the Californian mountains near his home with a few of his closest mates.

Prince Harry, 39, is set to tackle the Montecito peak which is part of the Cold Spring Trail in California, just a few miles from the mansion he shares with wife Meghan and their two children, Prince Archie, 5, and Princess Lilibet, 3.

“The Cold Spring Trail has lots of streams and pools which people regularly take a dip in,” said the source. “But there are also lots of snakes and other wildlife to contend with, like large cats.

“Harry and his friends will truly experience the outdoors as they take on one of the long hikes. Let’s hope he’s taking an experienced guide with him.”

As he turns 40 on Sunday, sources close to the Duke reveal that he is looking ahead with excitement, eager to pursue the work he’s most passionate about – from continuing the success of the Invictus Games to promoting The Archewell Foundation around the world.

Prince Harry also announced an exciting new non-fiction series with Netflix this year as part of the Sussexes’ multi-year partnership.

Filmed primarily at the US Open Polo Championship in Wellington, Florida, at The USPA National Polo Centre and produced in collaboration with Boardwalk Pictures, the series will offer viewers exclusive behind-the-scenes access to the elite world of professional polo.

The Duke’s new projects come amid reports that Prince Harry and Meghan Markle are said to be planning a third foreign tour before the end of the year.

The destination is likely to be somewhere in Africa, with Botswana and Lesotho in consideration, where Prince Harry’s charity Sentebale operates.

Prince Harry and Meghan Markle’s tour of Colombia proved a hit and they are planning more trips (Image: Getty)

The Duke and Duchess of Sussex received positive publicity during their tours of Nigeria in May and Colombia last month.

Prince Harry is also set to embark on a solo trip to New York later this month to “advance a number of his patronages and philanthropic initiatives”.

The Duke’s trip is set to take place during UN General Assembly High-level Week and Climate Week, the latter of which runs from September 22 until September 29. He is also set to make an appearance at a Diana Award event, in memory of his late mother.

The Sussexes have been approached for comment.