Percy O’Brien was born in Dublin on 24 August 1887 and joined the Royal Navy in September 1903. He joined submarines as a Sub Lieutenant, after time in HMS MONTAGU and HMS OCEAN, in August 1908.
Having then served as First Lieutenant of HMS C17, he was appointed to command A10 in May 1911 and then B2 in October 1911. HMS B2 was lost (with only one survivor) in a collision with the liner SS AMERIKA off Dover on 4 October 1912.
There is a memorial plaque to Percy O’Brien in St Anne’s Church in Portsmouth. The plaque is in the southeast corner of the church above a small altar.