Oval miniature in watercolour, in an oval silver suspension frame with foliate decoration round the inner rims, front and back. It has a coiled metal mount for the suspension ring and ribbon, which is similar to that of a miniature of Cromwell by Cooper in the National Portrait Gallery and several others in the NMM, and a flat backplate engraved in cursive script 'Admiral Blake / by S.Cooper'. The sitter is shown bust-length, half-turned to his left, in gilt-studded armour, with his brown eyes glancing out to the viewer. His brown hair is worn long over his shoulders, parted on the left over a receding forehead, and he has a white neckcloth secured with a grey-blue ribbon in front. Behind is the open sea below a dark blue sky, with two ships visible on the horizon, one over each of the sitter's shoulders, but that on the right larger and with sails and indeterminate red flags more clearly drawn.

Blake was the greatest of the Parliamentary sea commanders, and only second to Drake as a national sea hero until Nelson supplanted him. Born in Bridgwater, he passed the first forty years of his life as a relatively obscure Somerset merchant. Briefly elected as the town's MP in 1640, it was the English Civil War that turned him in to a soldier – and eventually a sea commander. His strong resistance to a number of royalist sieges in south-west England first brought him to prominence and in 1649, following the execution of Charles I, he was appointed one of the first three Generals-at-Sea (with Richard Deane and Edward Popham), and was involved in attempts to crush the remnants of the Royalist fleet, commanded by Prince Rupert. This accomplished, he went on to take the Isles of Scilly and Jersey from the Royalists. Much of his subsequent naval service was in the Mediterranean, including against Barbary corsairs and the Turks. In the First Dutch War, 1652-54, he fought ferocious battles in the Channel and North Sea with Maarten Tromp (killed in 1653) and his Dutch successors, with mixed results but not to his personal detriment. He was also a member of the Parliamentary Admiralty Board and the Council of State, and died of fever off Portsmouth just as he arrived home from destroying a Spanish West Indian fleet at Santa Cruz, Tenerife, in 1657. Buried in Westminster Abbey, his body was dug up and cast into a common pit at the Restoration.

Samuel Cooper, 1609-72, was the finest miniaturist of the Commonwealth and Restoration period. This example shows characteristic directness of representation and is probably the only original likeness of Blake now known (though the status of a portrait in Wadham College, Oxford, remains to be checked). It is also of technical interest, in that the paint has thinned a little showing some of the under-drawing. However, compared to other examples of Cooper's work, the finish is quite rough and, though in his style, the traditional autograph attribution is perhaps questionable, as is the date. If from life it could only be about 1650-56, but it might be a subsequent but near-contemporary studio copy of a now lost original. It is not signed, though many of Cooper's miniatures are, and was purchased for the Museum by Sir James Caird through Spink's at the J. Pierpont Morgan sale at Christie's, London, on 24 June 1935 (lot 27). It is no.110 (plate 50) in vol. 1 of G.C. Williamson's catalogue of miniatures in the Pierpont Morgan Collection (Chiswick Press 1906), but without previous provenance: Williamson also expressed the view that the silver mount was contemporary with the image.