Cashmere by John Singer Sargent. Photo / Supplied

An Auckland interior designer and fine art collector is suing a London dealer for $16million after he allegedly sold her paintings to a number of New York dealers and failed to hand over the proceeds.

Stephanie Overton has taken the legal action against one of Mayfair's most high-profile art dealers, Timothy Sammons.

Timothy Sammons, 59, set up his own fine art agency after being head of auctioneer Sotheby's Chinese art department.

Sammons, a trained solicitor, who also worked in the legal department at the auctioneer, operated as a well-connected agent, matching up private buyers with discreet sellers.

Wealthy clients used him as an agent to sell masterpieces by artists such as Van Gogh, Canaletto, Picasso, Chagall, Modigliani and Magritte.

He brokered the sale of John Singer Sargent's painting Cashmere to the Bill Gates Foundation for a record-breaking £6.7 million in 1996, and became a trusted confidant both to aristocratic families and to many of the world's most discreetly well-heeled collectors.

He seemingly guided them through the myriad obstacles of purchasing high-end artworks and helping them build their collections.

Sammons' website - now taken down - boasted that his company, Timothy Sammons Ltd, would give "impartial, independent and professional advice on buying, selling and owning art".

Clients trusted him and the dealers and auction houses loved the business he brought - he often consigned works for auction under his own name to maintain client anonymity.

However, in a case being heard at the High Court, Sammons is being sued by the WH Smith family trust - the leading beneficiary is Maria Carmela, Viscountess Hambleden, whose son, the present Viscount, is the long-time partner of Abba star Frida Lyngstad.

The trust is trying to recover a £1.6 million Canaletto Sammons sold on her behalf last year and failed to remit the money.

In a second case being heard in London and New York, Ms Overton - a New Zealand collector - is trying to recover NZ$16.5m (7.1 million British pounds) from Sammons after he allegedly sold her paintings to a number of New York dealers and failed to hand over the proceeds.

Some of the artworks owned by Ms Overton were modern classics by some of the world's most recognisable artists.

The paintings include Pablo Picasso's 'Buste de Femme', Marc Chagall's 'Reverie', René Magritte's 'La Geante', Amedeo Modigliani's 'Caryaide', Raoul Dufy's 'Syracuse', Lucio Fontana's 'Concetto Spaziale, Aattese', Henry Moore's 'Reclining Nude', and Tom Wesselmann's 'Collage Study for the Mouth, No. 10', according to Courthouse News Service.

The news service reports that the lawsuit claims eight New York-based art companies allegedly bought the works that they should have known were improperly offered for sale by non-party Timothy Sammons, Inc., an Upper East Side fine-art agency.

"At no time was TSI was ever authorised to complete a sale for any or all of the works," Ms Overton says in her complaint.

Courthouse News Service reports that Ms Overton has tried to get the works back from the defendants but "has been stonewalled in her efforts to determine the current locations of the works and if any of the defendants have attempted to transfer title to the works to other third parties".

"Defendants were not buyers in good faith and were not buyers in the ordinary course of business and, as such, defendants did not acquire any right, title or interest in any of the works," her complaint states.

Lady Corinne Green is suing over a series of Henry Moore pictures, although in her case she is suing Andrew Rose, the dealer who sold the pictures on behalf of Sammons.

And in New York, Sotheby's is a joint defendant with Sammons in a case brought by Houston Cummings.

It alleges that Sammons consigned Van Gogh's Cows In The Meadow on its behalf to the auction house, which sold it last June for £458,000. Sotheby's then paid Sammons, who has not paid Cummings.

Sammons, who lives in a £5.7 million mansion in Primrose Hill, North London, has had assets worth £7 million frozen and his passport confiscated by the High Court. The court has given him an allowance of £750 a week to live on.

His company, Timothy Sammons Limited, was made bankrupt in February this year by Her Majesty's Revenue & Customs.

It is not known what sum was owed, but as recently as October last year, the firm showed net assets of more than £1.8 million.

The company had offices in Mayfair and New York. One fellow dealer said: "Sammons was pretty flash and he spent a fortune decorating and renovating his Mayfair offices.

"He lived high on the hog but I don't think anyone had any suspicions he was unreliable. It is very embarrassing for all concerned."

According to Houston Cummings's lawyer, the telephone lines into the dealer's Manhattan office have been disconnected and the business his client was dealing with, Timothy Sammons Inc, is not an incorporated entity so had been trading illegally.

Sammons has been a well-known London art world figure for many years. Lark Mason, a New York-based auctioneer, who worked with him at Sotheby's, said: "I liked him very much. We worked together in the 1980s in the Chinese art department.

"After I left I did some specialist appraiser work for Sammons. My experience with him was always favourable, but I was not privy to the transactions or his business dealings."

He added: "The whole thing is pretty shocking because this is not the person I knew. The business that I had with him worked out fine but I guess there are a lot of victims out there who are hoping to get their money back who are now feeling very foolish."

- Mail on Sunday

- With additional reporting from Kurt Bayer, NZME. News Service