This painting is based on an engraving from a more contemporary painting by Samuel Scott (see PAH7667). In the summer of 1739, during a debate in the House of Commons relating to the deteriorating situation with Spain in the West Indies, Captain Edward Vernon claimed he could take the Spanish town of Puerto Bello, Panama, on the north side of the Isthmus of Darien with six ships of the line. He was taken at his word, promoted to Vice-Admiral and given six ships to redeem his pledge. The war became known as the War of Jenkins' Ear. The main obstacle to be overcome was the Iron Castle at the northern side of the entrance to the harbour. Vernon succeeded in taking the town and in destroying the fortifications and the iron ordnance.

This painting shows the attack on the Iron Castle. In the left foreground Vernon's flagship, 'Burford', 70 guns, with Vernon's blue Vice-Admiral's flag at the fore, in starboard-quarter view, engages the Iron Castle to port and two of the boats are moving in to make a landing. Ahead of her are the 'Strafford', 60 guns, and the 'Worcester', 60 guns, with Commodore Brown in the 'Hampton Court', 70 guns, on their right, flying his red swallow-tail pennant. Puerto Bello can be seen in the right background with gunfire coming from the castle. All the Union flags are incorrectly shown as being of the post-1801 pattern.

The painting was commissioned from Chambers by E.H. Locker, Secretary and Commissioner of Greenwich Hospital, who presented it to the Naval Gallery of the Hospital in 1838.

Chambers, the son of a poor mariner in Whitby, Yorkshire, followed his father to sea at the age of ten. After several years he became apprenticed to a house and ship painter, where his skill at lettering and marking whale-boats attracted attention. He was greatly admired for the details of his marine paintings, particularly those showing details of the crew performing naval tasks. Following his arrival in London, Chambers initially copied history paintings and then received many new commissions, including several from William IV. The painting is signed by the artist lower left 'G Chambers'.