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They include this 18th century English school oval portrait silhouette of the pioneering manufacturer Matthew Boulton (1728-1809).

The 5¼ x 4in (13 x 10cm) black gouache over pencil silhouette on an orange ground is inscribed Boulton of Soho House - a reference to Boulton's home of 43 years in Handsworth, Birmingham.

The source of the miniature, recently unearthed in one of the estate buildings, is not surprising: Matthew Boulton's son Matthew Robinson Boulton (1770-1842) bought Great Tew in 1815, famously commissioning London cabinetmaker George Bullock (1777-1818) to furnish the main house.