Enterprise was completed with a prototype twin 6 in (150 mm) turret in place of her two forward single mounts.

The turret installation occupied less space than the superimposed 'A' and 'B' guns of Emerald; the bridge was placed further forward.

Notwithstanding their age and outlandish appearance, the two ships were the fastest cruisers in the Royal Navy at the outbreak of World War II, Emerald exceeding 32 kn (59 km/h; 37 mph) in a full-power trial at full load in 1939.

They were also large enough that they could accommodate significant additions to their anti-aircraft armament as well as modern radar suites.

Later proposals to increase the AA armament by the addition of twin 4-inch and multiple 2-pounder pom-poms were thwarted by the outbreak of war.

Unlike almost all of the other older cruisers, both ships had active employment until the last few months of the war, in almost every theatre.

Emerald supported British forces in their campaign putting down the pro-German revolt in Iraq in the summer of 1941.

Both cruisers were reduced to reserve by January 1945; Enterprise was reactivated for use in trooping duties upon the ending of the war.