The Victorians had a thing about glasshouses. There was the Crystal Palace, built in Hyde Park for the 1851 Great Exhibition, later moved from its original site to Sydenham, where it finally expired in a heap of molten iron and glass in 1936. Then there was Joseph Paxton’s Great Stove at Chatsworth, which survived from 1840 until 1920, when its owner, the Duke of Devonshire, infuriated by government restrictions on the use of fuel for heating introduced during the First World War, deliberately had it pulled down. But the most memorable glasshouse of all, the biggest, most innovative and most expensive, is still very much with us, 180 years after the first stunned visitors strolled into its steamy expanse. Crouching like some gigantic ice sculpture in the centre of Kew Gardens, the Palm House is a testament to the engineering and scientific achievements of the Victorian age.