Submariner from HMS Taku making an addition to the ship's Jolly Roger, c. 1940-1944.
I recently learned that the Royal Navy has a tradition of carrying Jolly Roger flags on submarines that dates back to the start of the 20th century.
When submarines were first adopted by several European navies, the First Sea Lord (head of the Navy) Admiral Sir Arthur Wilson commented that in his opinion, submarines were "underhanded, unfair, and damned un-English", and any captured enemy submariners should be hung as pirates.
In the early months of WWI, after the British submarine HMS E9 successfully torpedoed a German cruiser, the submarine's commander Max Horton remembered those comments and had his signaller make a Jolly Roger that the submarine flew as it came into port.
Over time other submarines adopted the practice, with the initial idea of having a new flag for each successful patrol replaced by sewing bars onto the flag each time the submarine sunk a ship. This tradition was restarted in WWII and continues today, with some ships acquiring unique symbols on their flags - for example HMS Sickle adding an ace of spades after a torpedo they fired missed its target and hit a cliff in Monte Carlo, the explosion breaking all the windows of a nearby casino; or HMS Proteus having a can opener to commemorate surviving being rammed by an Italian destroyer (the destroyer came off worse).













