At the head was Captain Alexander Farrington, under whose directions several ships had been fitted out at Scapa with great ingenuity and success.

Every class of ship was brought into the service: steam cargo vessels, trawlers, drifters, sailing ships, ketches, and sloops specially designed to have the appearance of cargo ships.

These latter vessels were known as "convoy sloops" to distinguish them from the ordinary sloop.

Their design, which was very clever, had been prepared in 1916 by Sir Eustace T.D'Eyncourt, the Director of Naval Construction.

The enemy submarine commanders, however, became so wary owing to the successes of decoy ships that they would not come to the surface until they had inspected ships very closely in the submerged condition, and the fine lines of the convoy sloops gave them away under close inspection.
In the early spring of 1917 the Director of Naval Construction was asked whether the "P" class of patrol boats then under construction could be altered to work as decoy vessels, as owing to their light draught they would be almost immune from torpedo attack.
A very good design was produced, and some of the later patrol boats were converted and called "P Q's." These vessels had the appearance of small merchant ships at a cursory glance.