In my time in the Civil Service (after 12 years RAF service) I met an old chap who had been in the Royal Navy in 1944. After his initial training as a Telegraphist at HMS Mercury (Hampshire) he was posted to a ship in Scapa Flow (Orkney). The journey north took 3 days in crowded trains and a very rough crossing of the Pentland Firth. On arrival at his ship he was told that he had to attend a specialist course commencing in 7 days time - at HMS Mercury.