Without waiting for the _Mars_, Walker put to sea on April 19th, 1745, and a month later fell in with the privateer _Sheerness_, Captain Parnell, and kept company during the night. At daybreak, being then fifty miles west of the Lizard, they sighted eight vessels, evidently in company, and gave chase. The _Boscawen_ left the other astern, and about nine o'clock the enemy formed line, and were soon made out to be armed vessels, awaiting attack. This was odds enough to discourage most men, and the _Sheerness_ being hopelessly astern, no one imagined that Walker intended engaging, though all preparation was made for action.
Reading some suspense and anxiety in the faces of his officers, Walker called them together and addressed them: "Gentlemen, I hope you do not think the number of prizes before us too many. Be assured, by their being armed, they have something on board them worth defending; for I take them to be merchantmen with letters of marque, and homeward bound. Without doubt we shall meet with some opposition, in which I have not the least doubt of your courage; but I see we must here conquer also by a mastership of skill. Be cool, and recollect every man his best senses; for, as we shall be pressed on all sides, let every man do his best in engaging the enemy he sees before him, and then one side need not fear nor take thought for the other. In a word, gentlemen, if you give me your voice for my leading you on, I pawn my life to you, I will bring you off victorious."
Was ever a more masterly speech from a chief to his subordinates? But one reply was possible; the men went to their quarters and the _Boscawen_ sailed on into the thick of the enemy's line, strict orders being issued that, whatever fire they might receive, not a shot was to be returned until the captain gave the word. There were, unfortunately, sixty men sick, and these, with the exception of three, crawled on deck to render what assistance they could, or at least to see the fun.
Steering straight for the largest vessel, though already considerably damaged aloft by the fire of the others, Walker delivered his broadside, and then the enemy got round him, two on either side, one ahead and one astern; the other two apparently decamped, and took no part in the action. The ship astern, after attempting to rake the _Boscawen_, was so roughly handled by her stern guns that she hauled off, and struck her colours. The fight was continued with the remaining five for the space of an hour; and the writer asserts that it was maintained on board the _Boscawen_ without any confusion or disorder, the men, under the officers' orders, banging away at whatever happened to be in front of their guns, "without fear or thought for the others." The flagship struck, and sank ten minutes later; the remaining four stuck to it, hoping yet to subdue the sorely battered _Boscawen_; but Walker's men remembered his pledge to them, and were resolved that he should not be stultified. In another half-hour every flag was down, and the _Sheerness_, at length coming up, chased and captured one of the runaways; so the "bag" was one sunk and six captured.