William Perrin was born on 10 February 1874, and lost his father at a very early age. His education was thus limited, and he progressed through hard work and industry. He entered the Civil Service by examination and was posted to the Admiralty on 2 August 1893, serving first in the Record Office, where he acquired an aptitude for original research, and later in the legal branch, where he developed an interest in flag questions, upon which he became a recognised authority, and wrote the standard work. In December 1900 he became private secretary to Sir Evan MacGregor, Secretary to the Admiralty, and then to his successor, Sir Inigo Thomas. His services here were recognised by the First Sea Lord, Jackie Fisher, with a glowing tribute.
He was appointed Librarian at the Admiralty on 10 April 1908. The completion of the Admiralty arch over the Mall afforded accommodation for the reorganisation of the Library, and Perrin was the ideal man to undertake this. He gathered from attics and disused rooms throughout the Admiralty many volumes lying idle and uncared for, giving them a proper home, and took in hand the task of compiling an catalogue. Within two years he had succeeded to such an extent that his work was recognised in a special article in The Times on 16 September 1910, which referred to the transfer of some 5,000 volumes to their new, spacious and well-lit apartments. A year later a new reading room attached to the Library was opened by the First Lord, Reginald McKenna.
From 1922 until his death on 12 February 1931 Perrin was Honorary editor of The Mariner’s Mirror and honorary secretary of the Navy Records Society, and, by appointment of the Admiralty, secretary to the Trustees of the National Maritime Museum and the Macpherson Collection. His death was brought on by overwork, causing a breakdown in January, swiftly leading to his death.