The 1971 mystery entry
One detail in the logbook had attracted less attention than the others, mostly because it appeared on the final page and seemed, at first, like a clerical anomaly. After the last wartime entry in November 1943, there were twenty-seven blank pages. And then, on the very last page of the book, a single line in handwriting that analysis would later confirm was different from Voss’s. It was written in English, in a neat, unhurried hand, and it said: Completed. See file AR-7. H. The entry was dated 3rd September 1971.
Someone had gone back to the submarine. Twenty-eight years after the war ended, someone had descended through that hatch into the sealed dark, written one line in the logbook, and left. File AR-7 was never found—not in the crate, not in any archive. The initial H matched no name in any record connected to the original project.
What had been completed in 1971 remained, and perhaps would always remain, a mystery. But the acoustic technology described in those wartime pages had been filed as a patent in the United Kingdom on 3rd September 1971. The applicant was listed as a private firm with a registered address that no longer existed.
