Diadem Class first class protected cruisers

The Diadem Class first class protected cruisers were smaller versions of the Powerful class ships. The two ships in that class had proved to be too large and too expensive, and the Russian threat they were built to counter never emerged.

The Diadem class cruisers were lighter and shorter than their predecessors. 3000 tonnes were saved by reducing the number of Belleville boilers from 48 to 30. Engine output was reduced from 25,000 ihp to 18,000 ihp (in the last four ships in the class), a drop of 28%, but that was more than matched by the 45% drop in weight, and in tests the Diadem class ships were only 1 knot slower than the Powerful class.

Other changes including the replacement of the turret mounted 9.2in guns by four single 6i shielded guns fore and aft, a much criticised feature but one they would share with the later Monmouth class. The full length boat deck of the Powerful class was replaced by a three-quarter length forecastle which stopped just before the rear twin guns. Otherwise they were very close to the previous class.

The resulting ships required 200 less crew than the Powerful class ships, and cost £100,000 less per ship. They had a rather more active career than the two Powerful class ships, both of which entered the reserve after refits in 1902-1904. Four of the Diadem class spend significant parts of their pre-war career serving overseas, but by 1914 most had spent some time in the reserve.

The Diadem class ships were obsolescent at the start of the First World War. In 1914 three joined the 9th Cruiser Squadron, serving from Cape Finisterre at the north west tip of Spain down to the Cape Verde islands off the west coast of Africa (to June 1915). Three spent the war as training ships, two as minelayers, one as a hospital ship. HMS Europa had the longest active career, serving as the flagship at Mudros, the small port on the island of Lemnos used as the allied base during the blockade of the Dardanelles from 1915-1919.

Displacement (loaded)


Top Speed


Armour – deck


 - casemates


 - 6in gun shields


 - ammo hoists


 - conning tower





Sixteen 6in quick firing guns
Fourteen 12pdr quick firing guns
Three 3pdr quick firing guns
Three 18in torpedo tubes, 1 above water on the stern, 2 submerged broadside. 

Crew complement






Ships in class

HMS Amphitrite
HMS Andromeda
HMS Argonaut
HMS Ariadne
HMS Diadem
HMS Europa
HMS Niobe
HMS Spartiate

Books on the First World War | Subject Index: First World War

How to cite this article: Rickard, J (10 September 2007), Diadem Class first class protected cruisers , http://www.historyofwar.org/articles/weapons_diadem_class_cruisers.html

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