The remaining three destroyers, ordered from Laird (Express), J & G Thomson (Arab) and Thornycroft (Albatross) were "specials", which were required to reach higher speeds.

Four coal-fired Normand boilers fed steam at 240 pounds per square inch (1,700 kPa) to two triple expansion engines rated at 9,250 indicated horsepower (6,900 kW).

[4] Up to 140 long tons (140 t) of coal were carried, sufficient to give an endurance of 1,470 nautical miles (2,720 km; 1,690 mi) at 11 knots (20 km/h; 13 mph).

It was eventually decided by the Admiralty to accept Express despite this failure in recognition of Laird's great efforts and expense in trying to reach the over-optimistic requirement, and the fact that forcing the ship's machinery further was likely to cause excessive wear.

[10] Express collided with the stores ship RFA Aquarius in December 1907 at Lamlash, Isle of Arran, Scotland.

[13] On 30 August 1912 the Admiralty directed all destroyers were to be grouped into classes designated by letters based on contract speed and appearance.