From Helena Smith's piece in the Guardian:
It emerged in London in 1980 when a British Byzantinist, Professor Robin Cormack, spotted it in a suitcase in a restorer's atelier. It had been touched up by the looters to make it more saleable in the underground art market."It had been cut in two by the looters. Seeing what it was, Robin realised it must have been stolen and advised them to return it to Greece," said the cultural attache at the Greek embassy in London, Victoria Solomonides, who travelled with the icon to Greece."That did not happen and 10 years later the plot thickened when he was called by the British Museum to value an icon. It was the same one."On the advice of Cormack, curator of the Byzantium exhibition currently on at the Royal Academy of Arts, the British Museum decided not to buy the icon.
It seems then in 2002 a Greek art dealer offered to sell the work to the Benakis Museum in Athens for £500,000. It seems the High Court has ordered the return of the work in a proceeding "Six weeks ago". I've attempted to track donw the ruling this morning on baili.org, but I suspect the ruling is unpublished. If any of my kind UK readers could confirm this, I would be most grateful.