According to his naval record, Patrick Brennan was born on 17 March 1886 at Cloyne, County Cork, but birth registry and census documents indicate he was a year younger than this.  His parents were James Brennan, a labourer, and his wife Johanna (“Hannah”). Patrick was the eldest of four children.

He joined the boys’ training ship HMS NORTHAMPTON in June 1903 and continued training in her tender, HMS CALLIOPE.  In January 1904 he joined the protected cruiser HMS PROMETHEUS where he was rated Ordinary Seaman on his supposed 18th birthday, and later that year joined the cruiser HMS THESEUS.  In December 1904 he joined the new armoured cruiser HMS CORNWALL on commissioning, and was rated Able Seaman in September 1905. During 1907 and 1908 he was based at Devonport naval barracks, including training in HMS DEFIANCE as a Torpedoman.  In January 1909 he joined the torpedo-boat depot ship at Malta, HMS ORION, subsequently renamed as HMS ORONTES. In April 1911 he was back at Devonport in the pre-dreadnought battleship HMS CAESAR, transferring to the dreadnought battleship HMS COLLINGWOOD in March 1912.

In January 1914 he joined the submarine depot ship HMS FORTH, subsequently transferring to HMS DOLPHIN and then HMS MAIDSTONE which was to be the principal depot ship for the large Eighth Submarine Flotilla at Harwich during WW1.  HMS E15 was commissioned in October 1914, and it is likely that Brennan joined her at this stage.

On 27 March 1915, the depot ship HMS ADAMANT left Harwich in company with HMS E11, E14 and E15 to join the Mediterranean Submarine Flotilla. E15 was the first submarine to attempt to penetrate the Dardanelles in order to be able to disrupt the Turkish supply lines to the Gallipoli peninsula.  The attempt failed when unexpected currents forced the boat aground, and she came under Turkish attack. The Commanding Officer and five of the crew were killed on 17 April 1915 and the remainder of the crew, including AB Brennan were captured.  His service record states that he died ‘on 2 March 1917 while interned as a prisoner of war in Turkey’.  He was buried locally at Afion Karahissar but after the war was re-interred at Baghdad (North Gate) War Cemetery, Iraq.