It's one of the lesser known but most fascinating tales of World War One. What was the British government doing buying paintings at a Paris auction house while German guns were bombarding the city? And how did a priceless masterpiece by Cezanne come to find itself in a hedge by a Sussex farm track?

Maynard Keynes (he never used the John) is best known as a great economist, who believed strongly in state intervention in the market. He helped found both the World Bank and the International Monetary Fund. But less well-known is that he was a key member of the Bloomsbury Group, an avid art collector and the founder of the Arts Council.

A strange combination of events in 1918 allowed Keynes, then a humble Treasury adviser, to combine his two great passions, money and art.