Ordered under the Naval Defence Act of 1889, which established the "Two-Power Standard", the class was contemporary with the first torpedo boat destroyers.

[3] HMS Halcyon was commissioned to serve at the Mediterranean Station by Commander Scott W. A. Hamilton Gray in March 1898.

She was stationed at Souda Bay in early March 1900,[5] but later the same month left for Port Said to temporary relieve HMS Rupert as coast defence ship.

[9] “Halcyon, perhaps the smallest and least formidable vessel that ever crept into the ‘Navy List’ [sic], engaged the enemy imperturbably when they fled, losing one man from a fragment of shell, though practically unhurt herself.

Private letters speak of salvoes falling short and over in the most disconcerting manner, and of the ship being so drenched with water as to be in danger of foundering.”[10] On 29 July 1917, Halcyon spotted a periscope near the Smiths Knoll buoy east of Yarmouth, and carried out a ramming attack, followed by dropping two depth charges.