 For the Royal Navy one of the most immediate concerns was to contain the French Atlantic Fleet based in the massively fortified harbour at Brest in Brittany.This port was ideally positioned to disrupt the merchant shipping convoys that passed through the Celtic Sea and the Bay of Biscay "en route" to Britain from all over the world, and it was therefore imperative that the French fleet was not permitted to put to sea without being challenged.For the French, Brest was a vital port for the receipt of grain supplies from the Americas and so French fleets regularly sailed on missions to escort these convoys into the harbour and to disrupt British convoys entering the English Channel.