Coordinates: 48°23'24"N 4°29'24"W
Brest was an important city and harbour in the Napoleonic wars. It was the main French naval base on the Atlantic, and a key place for the Royal Navy to blockade.
Les Fillettes, literally, 'the Girls', are a group of submerged rocks in the middle of the fairway on the Goulet de Brest, causing a navigational hazard when approaching or leaving the harbour.
After a battle in which the French brig Espérance was taken as a prize, the blockading fleet fled before a storm to Tor Bay during the court martial of Barry McCool, deserter. The fleet returned to Brest and the Bay of Biscay after the storm.
Hotspur, Commander Hornblower commanding, is assigned by Admiral William Cornwallis to 'look into Brest' to determine progress of the French fleet and its state of readiness as the Peace of Amiens draws to a close, and to keep Cornwallis informed. Much of the book is set in the approaches to Brest.