Letters to submarines
Men on submarines usually receive comunication from home or 'familygrams' via teleprinter machines. However there have also been some more unusual ways:
The Deep Submergence Rescue Vehicle (DSRV), Avalon, completed an exercise in May 1979 to undertake the first transfer of men from one submarine to another whilst submerged.
The Navy also transferred this envelope in the same manner, originally posting it from Balloch Dunbartonshire to HMS Repulse before sending it via the DSRV Avalon to HMS Odin and then lastly to Clyde Submarine base. A submariner later posted the letter at Helensburgh Post Office.