This seems a bit off-topic for the thread, so I have replied to Robert privately.
Forum: WWI forum

Great progress, Michael. I'm reliant on you to research further, because Uboat records are completely new territory as far as my research experience is concerned. Regarding the map grid, the archivist at the UK Hydrographic Office in Taunton reckons he's onto something, but enquiries at the National Maritime Museum (Greenwich) drew a blank. Chris
Forum: WWI forum

Great stuff, Michael. And so quickly, too! Overnight, I think I've come up with the way of decoding these five-character abbreviations of Lat/Long. Your data from ADM239/26 is a codebreaker's dream, providing a 'crib' of a correct answer. I'll be back at TNA Kew later today trying it out on a full-size Admiralty Chart. What we seem to have here, as well as a recor
Forum: WWI forum

According to the records of No.14 Group, RAF, a hostile submarine was attacked by 255 Squadron at 09:35 on 14 August 1918, resulting in air bubbles and an oil slick. Location is given as "67ISC", which appears to be a map grid system used for information exchange between RAF and Royal Navy. Best approximate position I can give is 10 nautical miles south of Caldey Island. Two questions:
Forum: WWI forum