 In an early case of a single builder taking responsibility for building an entire class, contracts for these first six vessels were all awarded to the John Elder & Company at Govan on the Clyde.They were all fitted with 3-cylinder compound engines, with one high-pressure cylinder of 46 inches diameter being flanked by two low-pressure cylinders of 64 inches diameter.Two to three years later, the Admiralty ordered an additional three vessels to be built to the same design.