John Henderson's advisors have spoken exclusively to Antiques Trade Gazette  of how they are waiting to meet Roberto Matarazzo, the Naples lawyer of the 70-year-old retired Fiat factory worker from Sicily who reportedly bought the two paintings - by Paul Gauguin and Pierre Bonnard - for 45,000 lire, the equivalent of around £20 in today's money, at an auction of lost property in Turin in 1975.

Still Life with a Small Dog, by Gauguin, dating to 1889, is valued at £25m, while Woman with Two Armchairs, by Bonnard, is worth £500,000.

The revelations of the Italian buyer's luck sparked international media coverage when the story broke at the beginning of April last year.

Carabinieri alerted to paintings

According to Rome public prosecutor Marcello Cascini, the carabinieri were alerted to the paintings when a friend of the Italian buyer tried to sell them. That intervention led to the public revelations and ensuing media coverage, which detailed how the artworks came into the Italian buyer's possession and how he kept them on the wall at his home for 40 years.

Mr Cascini has explained to Mr Henderson's advisors that the judicial review that followed led to the works being returned to the Italian buyer on the basis of the Italian civil code. That grants ownership to holders of artworks after ten years if they are not aware that they have been stolen and after 20 years if they are.

However, Mr Henderson is preparing to challenge the decision under English law where there are no such time restrictions under the criminal code and, if successful, hopes that European Union regulations would overrule the Italian courts and enforce his claim.

He is the heir of the late Terence Kennedy, an American author whose wife was Mathilda Marks, the Marks and Spencer heiress who died in 1964.

Exhibition catalogues, newspaper reports and magazine articles, as well as Mathilda Marks' will and the picture frames from which the pictures were removed, with detailed labels on the back, place the two pictures firmly in their ownership - it is thought they were the buyers when Sotheby's sold the Gauguin on June 28, 1961.

When Mathilda Marks died she left her husband her entire estate, including the pictures, which remained in his possession until stolen in a high-profile burglary at his Chester Terrace home in Regents Park in June 1970. The thieves, posing as a policeman and two workmen, arrived at the house on the pretext of fitting a burglar alarm, removing the pictures from their frames during the few minutes the housekeeper took to make them a cup of tea.

International media coverage of burglary

What happened next is not clear, but Mr Henderson's advisors have even managed to trace witnesses who knew Mr Kennedy at the time and remember the incident, which was reported on the front page of The Observer newspaper the day after the burglary as well as in The Times and the New York Times.

Soon after, the pictures were taken to Italy and then reportedly left on a train.

They were then thought to have been kept by the Turin lost property office for the next five years before the Italian buyer acquired them at the auction.

"What checks did the Italian authorities carry out at the point of recovery, when the theft was very much in the public consciousness thanks to the international media coverage?" asked Dick Ellis, director of the Art Management Group and a former head Scotland Yard's Art and Antiques Squad. He is a specialist in the field of art recovery who has become involved in the case.

Having closed the house in Chester Terrace, Mr Kennedy put the rest of his belongings in storage and moved to Switzerland.

While on a later visit to London he suffered a major stroke and was recovering in the South of France when in 1976 mutual friends asked Mr Henderson, then a young actor, to travel down and act as Mr Kennedy's personal assistant/secretary for a few months - essential as, having previously spoken five languages, Mr Kennedy now struggled to speak at all.

Henderson made sole heir

Mr Henderson helped him communicate and eventually recover his speech and with their shared interests in theatre, dance and art a strong bond developed and Mr Henderson stayed on continuing speech therapy with Mr Kennedy every morning for the rest of his life.

Mr Kennedy went on to live for more than 20 years, finally dying in 1997 and making Mr Henderson his sole heir under a will administered in Switzerland.

The terms of that will mean that all Mr Kennedy's possessions, whether in his keeping at the time or not, passed to Mr Henderson. That covers the stolen pictures.

Investigations have not uncovered any insurance payout being made on the pictures, so Mr Henderson retains title under English law.

Mr Ellis, who has notified Mr Matarazzo of the legal claim and warned him that his client should not attempt to sell the works, believes that proper due diligence was not carried out prior to the Italian sale of the paintings. He has shown Antiques Trade Gazette  evidence that would indicate the carabinieri may not have carried out a full investigation into the circumstances of the Italian buyer's acquisition of the works. Both potential shortcomings might have a material impact on the Italian ruling awarding the Italian buyer ownership, he argues.

As this report was filed, Mr Ellis and Mr Henderson's advisors were awaiting a reply from Mr Matarazzo arranging a meeting to discuss the matter in Naples.