BBC Antiques Roadshow expert Philip Mould's jealous rival and their cruel vendetta

The is known for its teatime revelations of long-forgotten family heirlooms and priceless charity shop finds. Each week, the loveable experts analyse guests' items and give their appraisals on the long-running programme. Since its debut in 1979, the evening show has kept their fallouts to a minimum - but in 2011 things took a turn.

In May that year, the art world was reeling with the revelation that Mark Weiss, one of Mayfair's most well-respected art dealers, was behind a campaign of persecution against gallery owner and TV expert Philip Mould. For two years, Mr Mould had endured false allegations of infidelity and financial difficulty, which ultimately spread to newspapers, clients and even online.

They threatened both his marriage and his business, until private detectives uncovered the culprit behind the cruel scheme. Their feud began back in 2007 when Weiss was one of the bidders battling it out for a portrait of Elizabeth I, which eventually went to Mould.

He also found four Gainsboroughs, one of which was found on eBay for £120 that he later sold for tens of thousands of pounds. The portraits expert also found a portrait at a London auction house in a terrible state of repair.

It turned out to be the only picture of Henry VII's sickly elder brother, Prince Arthur, which went on to fund his Kensington townhouse after its jaw-dropping sale. After this success, Mould went from strength to strength, from opening galleries to writing books - meanwhile Weiss faded into the background.

Shortly after Mould published his 2009 book Sleuth: The Amazing Quest For Last Art Treasures, an entry appeared on the dealer's Wikipedia page questioning his true abilities. It claimed: "Out of interest, what are the many 'celebrated lost works of art' that Mould has discovered?

"Judging from those promoted on his website and his books, apart from Prince Arthur, they are pretty motley selection. Most of the other London art dealers have demonstrably made far more genuinely celebrated discoveries."

The Weiss Gallery was listed among those dealers who had made far more important discoveries on the website. The entry was later taken down, but Weiss was apparently still seething from Mould's decision to move into his area of expertise.

Determined to take down his younger adversary, Mr Weiss reportedly informed the papers of Mr Mould's affair with Charlie Barton, an artist who counts Andrew Lloyd Webber and Prince Edward among her admirers.

The revelations about their relationship led to a temporary split between Mould and his wife Catherine. In autumn of 2009, he moved into Miss Barton's London home, leaving Catherine and their son Oliver. The couple reunited months later.

Just five months later, Mr Weiss struck again after the art dealer bought a picture attributed to Rubens at the auction house Bonhams with a fellow investor for £700,000. The art Press duly received a tip that the purchaser did not have the funds to pay for the painting.

This time, Weiss launched an attack on not just Mr Mould, but Dr Bader too - a highly-respected collector and philanthropist who owns five Rembrandts. It was at this point that he and Mr Mould brought in private investigators to look into the case.

They discovered that the author of the tip-off went under a pseudonym that matched the one used in the initial Wikipedia entry. They then proved that the person operating under the pseudonym was Mr Weiss.

When confronted with the evidence, Mr Weiss admitted that he was guilt and sent a letter of apology to the BBC antiques expert. Dr Bader told : "I don't know why he would make up such a story. I don't know Mr Weiss.

"He invited me and my wife to diner one evening many years ago. I don't dislike him, he's an able dealer, he has a nice-looking gallery and buys some good paintings, but I would not work with him, no.

"I've worked with Philip a long time and he is one of the most honest and honourable dealers there is. He really knows what he's doing." The antiques dealer remains a major player in Mayfair and continues to appear on the Antiques Roadshow alongside host Fiona Bruce.

Antiques Roadshow airs on Sundays from 7pm on BBC One or catch up on BBC iPlayer.