The Royal Navy, faced with increasing losses of merchant ships to U-boats, came up with the idea of using decoy ships to trap German submarines. They were eventually known as Q-ships after Queenstown, now Cobh, in Ireland, where many of them were based.
Early war U-boats carried only around six torpedoes, so their captains preferred to surface and sink smaller merchant ships by gunfire. A Q-ship would give the impression of being an innocuous tramp steamer. Her armament would be hidden inside false deck houses or lifeboats or on swivel mountings that could appear when needed. Most of her crew, who were volunteers, would also be concealed, with hidden alleyways and special trap doors allowing them to get to their action stations without being seen. The majority of the crew of a warship are concerned with fighting rather than sailing her, so Q-Ships had far larger crews than they would have had as merchantmen. The collier Loderer had a crew of about six officers and 25 men in merchant service and 11 officers and 56 men after being converted to the Q ship HMS Farnborough.
The first Q-ship to see action was HMS Prince Charles, a 373 ton collier that was given an armament of two 6 pounder guns, two 3 pounders and a number of rifles. Her civilian crew of Captain F. N. Maxwell and Chief Engineer Anderson and nine other men volunteered to remain on board. Lieutenant William Mark-Wardlaw RN was given command, with the crew being completed by Lieutenant J. G. Spencer RNR, two RN petty officers and nine RN ratings.
Prince Charles was a civilian ship under charter to the RN and based at Scapa Flow. The terms of her charter allowed her to defend herself. Mark-Wardlaw’s orders of 20 July 1915 from Admiral Sir Stanley Colville included the following clauses (the earlier ones describing the area in which he was to operate have been omitted):
‘The object of the cruise is to use the Prince Charles as a decoy, so that an enemy submarine should attack her with gun fire. It is not considered probable, owing to her small size, that a torpedo would be wasted on her.
In view of this, I wish to impress you to strictly observe the role of decoy. If an enemy’s submarine is sighted make every effort to escape, if she closes and fires, immediately stop your engines, and with the ship’s company (except the guns’ crews, who should most carefully be kept out of sight behind the bulwarks alongside their gun, and one engineer at the engines) commence to abandon ship. It is very important, if you can do so, to try and place your ship so th a t the enemy approaches you from the beam.
Allow the submarine to come as close as possible, and then open fire by order on whistle, hoisting your colours (red ensign).
It is quite possible that a submarine may be observing you through her periscope unseen by you, and therefore on no account should the guns crews on watch be standing about near their guns.
If by luck you should succeed in sinking a submarine, on no account are you to allow the information to leak out of your ship, the strictest precautions are to be taken on arrival in a harbour, or meeting a ship at sea, that none of the officers or men give away the information.’
Prince Charles left Scapa Flow at 8:00 pm on 21 July. In the early hours of 24 July she encountered a merchant ship stopped near a surfaced submarine 10 miles WNW of Rona. Mark-Wardlaw’s report stated that:
‘Shortly after this the submarine was observed to start her oil engine and proceed towards us at full speed. I then hoisted my ensign. At about 7.5 p.m., submarine being about 3 miles distant, 5 points on the port bow, she fired a shot which pitched about 1,000 yards over.
I then stopped engines, put ship’s head to swell from NNW, blew three blasts, and boat’s crews were ordered to get boats out.
All this time the submarine was coming very fast towards us (20 knots) and at 7.10 she fired a second shot which went between funnel and foremast and landed 50 yards over.
The submarine then turned so as to bring her broadside to us at about 600 yards, and as the submarine continued to fire and seeing that the range could not close any more, I opened fire with both port guns.
Directly I opened fire the gun’s crew of the submarine deserted their gun and entered conning tower and she apparently attempted to dive.’
The submarine, which was U36, was struck by a shell as she dived. She came back up, turning. Prince Charles closed to 300 yards and continued to fire, scoring several hits. U36’s crew abandoned ship, with 15 out of 33 men, including her captain, Kapitänleutnant Ernst Graeff, being saved by the British.
The steamer that had been near U36 when Prince Charles came upon them was Danish. Mark-Wardlaw suspected that she had been supplying the U-boat, so ordered her to follow him to port for inspection. The Danes turned out to be pro-British and delighted at the outcome of the action. They agreed to keep quiet about it and were released. 
U36 had sunk a Norwegian sailing ship and steamer, a French steamer, a Russian steamer and nine British trawlers during her cruise. She had also fired on but missed the armed merchant cruiser HMS Columbella and captured the US sailing ship Pass of Belhama, which was sent to Cuxhaven with her cargo of cotton. She later became the German commerce raider Seeadler, like Prince Charles an apparently innocuous vessel with a concealed armament.
 T. Bridgland, Sea Killers in Disguise: The Story of the Q Ships and Decoy Ships in the First World War (London: Leo Cooper, 1999), pp. 14-15.
 Ibid., pp. 8-9.
 Naval Staff Monograph (Historical) 1926 vol. xiv, Home Waters part v, July 1915 to October 1915. Appendix J, p. 220.
 Ibid., p. 37.
 Ibid., p. 38.
 Ibid., pp. 38-40.