In 2011, Mr Gryaznov moved to Courchevel, the French ski resort with a reputation for being a playground for the rich. There he worked in the kitchen at K2, a Michelin-starred restaurant favoured by Russian elites.

His friends in Paris, according to Le Monde, were unaware of his former life in Luxembourg.

It unravelled for the chef when he was picked up on the radars of several European intelligence services during a visit to Turkey, where he had arrived from Moscow.

On May 8, he was refused boarding on a plane from Istanbul to Paris for being too drunk, according to reports.

Instead, the 40-year-old took a taxi to the Bulgarian border, where he picked up another car to St Vlas, a resort on Bulgaria’s Black Sea Coast, where he owns property.

It was here at the dinner where Mr Gryaznov disclosed his identity and his assignment under the influence of alcohol, witnesses told the Insider.

He then travelled to Varna, a town 60 miles north, to catch a flight back to the French capital.

Before flying, Mr Gryaznov is said to have phoned his FSB handlers to inform them the operation was on track and that he had hired “one more Moldovan from Chisinau”.

It was this detail that piqued the interest of French investigators, because they have previously discovered Moldovans who have links to Russian espionage groups carrying out hybrid attacks in France.

Ironically, a former love interest once told him that “alcohol will get to you one day”.

Mr Gryaznov now faces up to 30 years in a French prison if he is found guilty.

Lord Skidelsky was contacted for comment.