On 20 November 1914 the
British Admiralty requisitioned
Ambrose for conversion into an AMC. She was armed with eight
4.7 inch guns and two
6-pounder guns, and commissioned on 10 December 1914 as HMS
Ambrose by Commander Charles William Bruton,
R.N., with the
pennant number M 87.
Ambrose served in the
10th Cruiser Squadron as part of the
Allied Blockade of Germany. She patrolled between the
British Isles,
Iceland and
Norway. On 11 March off the west coast of Scotland a submarine attacked
Ambrose three times. The first attack was at 1320 hrs, when a torpedo missed her bow by . The second attack was at 1405 hrs, when a torpedo passed astern of her. The third attack was at 1422 hrs. On each occasion
Ambrose opened fire on the periscope. After the third encounter the attacks ceased, and
Ambroses officers suspected that she had sunk the submarine. On 6 May submarines attacked
Ambrose off
Skerryvore.
Ambroses patrols with the 10th Cruiser Squadron ended in September 1915, when she reached port in
Glasgow. On 13 October she transferred to
Greenock and on 20 October her crew was paid off. Also on 20 October, the Admiralty bought
Ambrose from Booth Line. ==Submarine depot ship==