The unsettling ambiguity of La plaine de l’air (1940) by Magritte resonated strongly with critics when exhibited at Galerie Dietrich in Brussels in 1941. Painted at a moment when Europe was being engulfed by conflict it shows a single oversized leaf grafted onto a trunk set against a stark mountain landscape. The leaf, one of Magritte’s most distinctive and recurring motifs, introduces a solitary, watchful presence and channels all the tension of the early Second World War. Estimated at £3.5-£5.5 million (€4.03-€6.33 million) it features at Modern Visionaries – the Roger and Josette Vanthournout Collection at Christie’s in London on March 5 and 6 plus an online auction. Assembled over six decades their collection, with an overall estimate is in the region of £40 million (€46 million), spans almost 150 years and ranges from symbolism, Belgian expressionism and surrealism to post war avant garde, minimalism to modern and contemporary British art.