On April 29th he sighted a considerable fleet, which, however, he soon lost again. On the 30th he looked into Baltimore, and, seeing nothing there of the enemy, came to the conclusion that the French must be to the westward of him. He therefore bore away with an east wind for Cape Clear. In the evening he had the satisfaction of sighting the fleet of which he was in search. It was standing into Bantry Bay. Herbert lay in the offing for the night, and in the morning stood in after the foe.

This French fleet, consisting of twenty-four ships of the line, two "frigates" and ten fireships, had left Brest to carry to Ireland a quantity of stores and ammunition, and was under the orders of François-Louis de Rousselet, Comte de Chateaurenault, as Lieutenant-General, in the Ardent, 66, with the chefs d'escadre Jean Gabaret, in the Saint-Michel, 56, and Forant, in the Courageux, 56, as second and third in command. In addition to the force which had come directly from Brest, there were in the Bay three "frigates" under Captain Duquesne-Mosnier, who had been left behind by the previous expedition in order to serve the interests of James on the Irish coast. One of them was commanded by an English officer who had adhered to the late king in his misfortunes. The whole French force upon which Herbert descended consequently amounted to twenty-four ships of the line, few of which apparently mounted more than sixty guns, five " frigates," and ten fireships.

As Herbert went into the Bay on the morning of May 1st, Chateaurenault, who, according to French accounts, would have attacked earlier had he not desired to first land as many troops and stores as possible, weighed to meet the English. The latter, being to leeward, experienced some difficulty in working up towards the French, who, bore down in excellent order and began the engagement at about 10.30 A.M. When the English commander-in-chief saw the force of the enemy, and realised how disadvantageous for his own fleet would be an action to windward in waters so narrow, he put about and went out of the Bay under easy sail, so as to be able to manoeuvre, with a view, if possible, to gain the wind, and so as to bring his very indifferent line into something like order. The line was improved; but, owing to the caution of the French, the wind could not be gained. . The action continued, however, until about 5 P.M., and, in the course of it, the French ship Diamant, 54, commanded by the Marquis de Coetlogon, was most seriously damaged by an explosion of ammunition which had been accumulated in her captain's cabin. Towards the end of the battle the English had been so worsted that, but for two facts which told accidentally in their favour, Chateaurenault would, in all probability, have decisively defeated them. One was the absence of the French fireships, which were still landing stores in the Bay. The other was the jealousy with which the chefs d'escadre Gabaret and Forant regarded Chateaurenault, who was much their junior in point of service. These officers tacitly refused to press the advantage; and at length the French commander-in-chief found it prudent to tack and stand again towards the shore. Having completed his mission he returned to Brest on May 8th. In consequence of the battle, war between England and France was immediately declared.

Admiral Herbert, who thus narrowly escaped a crippling disaster, made for Portsmouth. His fleet had lost one captain, George Aylmer, one lieutenant, and ninety-four men killed, and about three hundred officers and men wounded. The English had not been so inferior as to render their action a brilliant one: the French success had scarcely been so pronounced as to be entitled to the name of victory; yet apparently both nations were satisfied. When King William visited Portsmouth a few days later he created Herbert Baron Herbert of Torbay and Earl of Torrington, knighted Captains Ashby and Shovell, presented each seaman with a gratuity of ten shillings, and made special provision for the widows of Captain Aylmer and others who had fallen. These royal attentions from the new monarch, to servants of the fidelity of many of whom he was still in much doubt, were, perhaps, politic; but it can hardly be said that they were all fully deserved.