A most unlikely service for Clan Line was that along the south west coast of North America.
The ships employed were equally unlikely, they were converted Flower Class sloops of The Royal Navy
The venture was a failure.
Full information can be found in Clan Line - Illustrated Fleet History
Q Ships were warships designed as merchantmen, their tactic was to lure a U-Boat to the surface and then engage with guns.
The Aubretia and the following Anchusa Class were extraordinary ships. Using the Flower hull and machinery commercial ship yards were given orders to construct ships along their own standard patterns upon the hull. Hence there is no standard to the designs, weapons were hidden in a variety of ways including mounting on reversing hatches, screened by drop shields and false deck houses.
Secrecy about the ships was very tight and there is little information to be had even to this day. They were however the first ships to be purpose built as Convoy Escorts and were classed as Convoy Sloops.
Displacement 1250 tons, 267 ft overall, 33.5 ft beam, 11-12 ft draught.
Armament varied but nominally 3 x 12 Pdr, 2 x 3 Pdr, in service generally 2 x 4" guns, a 3 Pdr and Depth Charge throwers.
Q-Ships were a violation of International Law but were considered justified due to U-Boat operating out of the law also. The tactic was an old one often used by the RN to lure enemy ships close to an armed merchantman, it was a matter of pride and old law that a ship showed it's real flag before opening fire.
The phrase has passed into general use: Showing your true Colours.