She was purpose built to support three of the new D-class submarines under the 1910/11 Naval Programme, allowing a small part of a flotilla to be deployed away from the main base.

[3] On 3 November 1914 Adamant was sent to Yarmouth to act as depot for a detachment of the Flotilla, which was based there from this date.

[5] In January 1916 Adamant moved to Brindisi as depot ship for the submarines of the Adriatic Squadron.

She returned as depot for the submarines of the Eastern Mediterranean Squadron at Mudros in November 1916.

In October 1917 she returned to the Adriatic Force as depot for submarines based at Govino (now Gouvia) on Corfu, moving back to Brindisi on 28 March 1918.