● The modern obsessions with the intertwined themes of art value and art theft can be traced back to 1876. Then, Thomas Agnew & Sons in London put on display Gainsborough’s bravura portrait of Georgiana, Duchess of Devonshire. The portrait was not just a spectacular work of art — as vivacious as its subject — but had just become the most expensive painting ever sold at auction.
The picture had not been seen for 50 years and had belonged to a Mrs Maginnis, who had thought nothing of chopping off the Duchess’s legs so that
