Lorient was at the heart of the Battle of the Atlantic, and Brian was very interested in visiting the site of the German submarine base that after intensive bombing by the British and US, and thousands of bombs dropped, was hardly damaged and is still standing today. And was actually used by the French Navy after liberation, until 1997.
Between Feb 1941 and Jan 1943, 15,000 workers built three enormous concrete bunkers from one million cubic meters of concrete.
The bunkers were each over 500 feet long, 400 feet wide and 67 feet high and could house up to 15 submarines each, and housed 1000 sub-mariners, and they were impenetrable, with a roof thickness of 25 feet!
Brian was in awe of these bunkers, the complexity of the structures, and that they were built in such a short time.