His opportunity arrived in 1739, when, during the War of Jenkins' Ear, he served under Vernon in the attack on Portobello, in the isthmus of Darien. He led the squadron into Boca Chica, placing his vessel, the "Hampton Court", alongside the strongest part of the fortifications. When the fortress surrendered, the Spanish governor presented his sword in token of submission. Brown very properly declined to receive it, saying he was but 'second in command,' and took the governor in his boat to Admiral Vernon. But the Spaniard was obstinate, declaring that but for the insupportable fire of the commodore he never would have yielded. Thereupon Vernon, very handsomely turning to Brown, presented to him the sword, which is still in the possession of his descendants. In 1741 Brown was appointed to the office of commissioner of the navy at Chatham, a situation which he held with unblemished reputation until his death, on 23 March 1753. His daughter, Lucy, became the wife of Admiral William Parry, commander-in-chief of the Leeward Islands; and her daughter and namesake married Captain William Locker, under whom Lord Nelson served in his early days, and who subsequently became lieutenant-governor of Greenwich Hospital. There was a portrait of Brown in the Painted Hall at Greenwich, which subsequently passed in the hands of the successor institution, the National Maritime Museum.