It has hitherto been supposed that, north of the Alps, the elaborate medieval mosaic work known as Cosmatesque was confined to Westminster Abbey. An example with glass tesserae, however, has now come to light from Wimborne Minster, Dorset. This paper explores the circumstances of the rediscovery there in the eighteenth and nineteenth centuries of pieces of ‘rich mosaic’, describes the surviving fragment and compares it in style and function to counterparts in Rome and in the Confessor's Chapel at Westminster. It concludes that it dates, like those at Westminster, to the 1270s or 1280s. It suggests that it adorned the shrine of Wimborne's Saxon founder, St Cuthburga, and that the patron who commissioned it was most likely Henry de Lacy, Earl of Lincoln, lord of the nearby manor of Kingston Lacy and close associate of Edward i.