During the Anglo-Spanish War (1654–1660), he won renown and a fortune in prize money when he captured a great part of the Spanish West Indian treasure fleet off Cadiz in 1656.
He was knighted by the Lord Protector Oliver Cromwell for services in Admiral Robert Blake's destruction of Spanish ships at Santa Cruz, 1657.
She was specially fitted out "for surprising small pickaroons that lurk among the sands" on the Essex coast,[4] and for convoy service in the North Sea.
[4] In August he captured the Robert, a small frigate, apparently one of Prince Rupert's vessels, for which and other good services he was awarded £20 and £5 for a gold medal.
He was certainly with the fleet in the following April, when he signed the declaration of the sea-officers on the dissolution of the Rump Parliament by Oliver Cromwell, which was, in fact, a resolution "not to meddle with state affairs, but to keep foreigners from fooling us".
[4] In September, when the sea-generals with the greater part of the fleet went to Aveiro, Stayner, then in the Speaker, was left off Cadiz in command of a small squadron of some six or seven ships.
[9] Shortly after this Stayner returned to England with Edward Montagu (later Earl of Sandwich); but rejoined Blake early the next year, and took a brilliant part in the destruction of the Spanish ships at Santa Cruz on 20 April.
Stayner was immediately detached to begin the attack, and being supported by Blake with the remainder of the fleet, the Spaniards were, in a very few hours, driven out of their ships and breast-works The former were instantly taken possession of by the English: and it being impossible to bring them off they were all set on fire and burnt to the water's edge.
[12] In the early summer of 1661 Stayner was again commander-in-chief in the Downs, and in June sailed for Lisbon and the Mediterranean as rear-admiral of the fleet under Montagu now the Earl of Sandwich.
[13] Then, when Sandwich went to Lisbon to take Catherine of Braganza to London, Stayner, with his flag in the Mary, remained as vice-admiral of the fleet under Sir John Lawson.