Thomson is a noted art collector and owns works by Rembrandt, J. M. W. Turner, Paul Klee, Hammershoi, Edvard Munch, Patrick Heron, Joseph Beuys, E. L. Kirchner, and Egon Schiele. Thomson owns the world's largest collection of paintings and drawings by the English painter John Constable. In an interview with Geraldine Norman in "The Independent" in 1994, Thomson said he bought his first Constable drawing at 19, giving the seller "an oil painting in exchange and quite a lot of money". Norman described him as a "fanatical collector", and Thomson described how he "fell in love" with Constable's style as a young child. In his twenties, Thomson stunned the art world with two monumental purchases. In 1984, he acquired J. M. W. Turner's spectacular 'Seascape: Folkestone", for a record £7.3 million (£21.8 million in 2017) from the sale of the collection of noted British art historian Kenneth Clark. The following year, Thomson, 27, broke another world record when he bought Rembrandt's monumental "Christ Presented to the People", from 1655, for a record £561,000 (£1.7 million in 2017) at Christie's London, when the Duke of Devonshire sold the Chatsworth Collection in one of the largest auctions of the time. Thomson sold both masterpieces within a few years during the 1980s financial crisis.