The fate of a major London exhibition of French and Russian paintings, halted by Moscow's culture ministry over fears the art could be seized while on British soil, has raised serious questions over the security of artworks and other state assets overseas.
By Robert Greenall
Many commentators have put the row down to a diplomatic spat between the two countries.
Shchukin collected over 250 works of art, many from Western Europe
But there are still genuine concerns arising from suggestions that some of the works could be subject to ownership claims, or that companies seeking the recovery of debt from the Russian government could take legal action to seize them.
From Russia: French and Russian Master Paintings had been due to open at the Royal Academy of Arts in January, following a spell in Duesseldorf, Germany.
Many of the works in the exhibition were confiscated from private collections by the Bolsheviks after the 1917 revolution, and there have been cases of descendants of the collectors trying to seek their return.
Textile magnates Ivan Morozov and Sergei Shchukin between them collected more than 300 artworks, including many by European artists like Picasso, Matisse and Gauguin, before fleeing Russia.
The Morozov family has never challenged the Soviet government's ownership of its collection, on the grounds that their ancestor had bequeathed his collections to the state before the revolution.
But a grandson of Sergei Shchukin, Andre-Marc Delocque-Fourcaud, has on three occasions tried unsuccessfully to recover some of the 258 paintings owned by his grandfather.
The Shchukin collection contains what has been described as the star of the current exhibition, Matisse's The Dance.
It is thought unlikely that Mr Delocque-Fourcaud will pursue his claims any further, as he appears to have made peace with the Russian authorities.
It is unclear whether any paintings in the exhibition not belonging to the two collections could be subject to similar claims.
But Russia's main fear is that the paintings, as valuable state assets, may be seized at the request of commercial organisations seeking to recover debts from Moscow.
In 2005, the Geneva-based import-export company Noga applied to a Swiss court to seize 82 paintings from St Petersburg's Hermitage Museum.
Matisse's The Dance is one of the highlights of the exhibition
The company claims it has been owed millions of dollars by the Russian government since 1990.
The paintings were held for a day before the Swiss government intervened and sent them back, but Noga has not dropped its claim.
The UK government has maintained that this could not happen in London, as the paintings are covered by 1978 legislation, the State Immunity Act, which safeguards all foreign state property in the UK.
But analysts say this act may not give the paintings immunity from debt recovery, and Moscow has been pressing the UK to pass legislation to this effect. Anti-seizure laws already exist in much of Europe.
The Tribunals, Courts and Enforcement Act, which received royal assent in July, had not been due to come into force until March, more than two months after the exhibition begins.
But, in response to Russia's decision to halt the exhibition, UK Culture Secretary James Purnell announced that the law was being brought forward to 7 January.