The distinguished collection of Old Master paintings held by the 2^nd Earl de Grey (1781–1859) at his London home of 4 St James’s Square had been formed by several generations of his ancestors. The purpose of this article is to trace the history of the collection, from the late seventeenth to the early nineteenth centuries, on the basis of a catalogue published by the earl himself in 1834. Attention is also paid to how the collection was displayed, and to its relationship with the collection mainly of portraits housed at the family seat of Wrest Park in Bedfordshire.