 At 00 : 30 hours on 28 March the convoy crossed over the <unk> at the mouth of the Loire estuary , with Campbeltown scraping the bottom twice . Each time she was able to pull free , and the group proceeded on up toward the harbour in darkness . They had got to within about eight minutes passage from the dock gates when at 01 : 22 the entire convoy was illuminated by the combined searchlights of both banks of the estuary . A naval signal light demanded their identification . 
