A three-quarter-length portrait to left in a breastplate over a leather jerkin, with a pink sash round his waist. His left hand is on his hip and his right rests on a rock with the sea beyond.

Having commanded several ships from 1661, in 1665 at the early age of 26 he was promoted to Rear-Admiral of the Red squadron under James, Duke of York. He was present at the Battle of Lowestoft, 1665, the first fleet action of the Second Dutch War, where James was in command. Berkeley was killed the following year during the Four Days' Fight. This happened on the first day when his flagship, the 'Swiftsure', 70 guns, was cut off and surrounded. He fought to the end and when almost alone on the quarter-deck was hit by a musket-ball in the throat. He was reported to have staggered into the captain's cabin and was found by the Dutch lying dead on the table. The portrait is confusingly inscribed 'Sir Will Bartlett' but is one of the 'flagmen' series commissioned by the Duke of York after the Battle of Lowestoft and noted by Pepys as being begun or finished when he visited Lely's studio on 18 April 1666.

Lely, a Dutchman who arrived in England in 1641 after the death of Van Dyck, soon became his successor as leading portraitist of the day. He worked for Charles I, continued to flourish under the Commonwealth and Protectorate, and after the Restoration of 1660 was appointed Principal Painter to Charles II. The full 'flagmen' set consists of thirteen individual portraits, of which George IV presented eleven plus a copy of that of Admiral Sir John Lawson (BHC2833) to Greenwich Hospital in 1824. The originals of Lawson and of Prince Rupert were retained in the Royal Collection, although William IV presented an extended full-length copy of the latter (BHC2990) to the Hospital in 1835.