Party boy Spencer Matthews to be best man at Pippa Middleton wedding

Pippa Middleton and James Matthews. Photo / Getty Images

He's the reality TV playboy who claims to have bedded more than 1000 women - and Spencer Matthews will be delivering the best man speech at a semi-royal wedding this weekend.

The younger brother of hedge fund investor James Matthews, who is marrying Catherine the Duchess of Cambridge's little sister Pippa Middleton today, is well known in Britain as a wild party boy who has been the leading star on a number of popular reality TV shows.

Ms Middleton has reportedly warned her soon-to-be brother-in-law to stay off social media at the event, and to 'tone down' his speech at the reception, with Royal guests in attendance including the heir to the throne Catherine's husband Prince William, their children Prince George, 3, and Princess Charlotte, 2, and Prince Harry.

The 27-year-old first shot to fame on the show Made In Chelsea in 2011, which followed the lives of young partygoers living in London's exclusive postcodes, and was a fan favourite before he was sensationally dropped after five seasons for steroid addiction.

He was painted as the "villain" of the show, who always seemed to have a new girlfriend and left a string of broken hearts in his wake.

His reputation took even more of a dive when he was filmed allegedly snorting cocaine in 2012 - allegations his management has steadfastly refused to comment on over the years.

Matthews has managed to stay in the spotlight over the years with stints on The Bachelor, The Jump and I'm A Celebrity: Get Me Out Of Here!, which filmed in Australia in 2015.

He only lasted two days filming in the jungle before producers became aware of his secret steroid addiction and booted him out of both I'm A Celebrity and Made In Chelsea.

But he relaunched his character this year on British challenge show The Jump, a wildly popular reality show in which celebrities take on winter sports challenges over 25 episodes.

Matthews was crowned overall winner of the fourth series of the show earlier this year, and he also seemed to have won in the love department, meeting his current girlfriend, Vogue Williams, during filming.

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Great event @virginiamacari x

A post shared by SPENCER (@spencermatthews) on May 7, 2017 at 12:16pm PDT

However Williams, 31, a model and reality star, has been black-listed from the society wedding of the year with British media reporting Pippa believed it was not necessary to invite her because the pair hadn't been dating long enough.

Matthews has made his £2.7 million (AU$4.7 million) fortune through his family's successful hotel business - his parents David and Jane Matthews own popular celebrity resort Eden Rock at St Barths - as well as his work as a PR manager and TV star.

He also penned a confronting autobiography in 2013 titled Confessions of a Chelsea Boy, in which he goes into details about a wild 'sixsome' he had with some 'nifty Canadian girls', as well as making the extreme claim he had slept with more than 1000 women and lost his virginity at 13.

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Cruising through Dublin and run into the one and only @voguewilliams... What a coincidence...

A post shared by SPENCER (@spencermatthews) on Mar 29, 2017 at 11:37am PDT

Despite his wild ways and lothario reputation, Matthews has had his fair share of heartache.

His older brother Michael, who is also James' sibling, tragically died in 1999 climbing Mount Everest, hours after becoming the youngest Briton to conquer the peak at age 22.

Matthews and his family created the Michael Matthews Foundation, which provides education to children by constructing school buildings in remote areas.