William Mitchell was born in 1878Q4 in the village of Downton, about 3 miles south of Salisbury, the fifth of six children of George Mitchell and his wife Ellen (née Bailey) who were farm labourers. 

In August 1895, William Mitchell attested for the local militia, the 3rd Battalion Wiltshire Regiment, giving his age as 17 years and 11 months, although actually a year younger.  But a few months later, he joined the Royal Navy at HMS BOSCAWEN on 31 January 1896, claiming a date of birth of 13 December 1879, although actually a year older. He served in the armoured cruiser HMS AUSTRALIA, and the battleship MARS, being rated Able Seaman in June 1899, and gaining  a Seaman Gunner 2nd Class qualification.  From Sep 1904 to June 1905 he served in the submarine depot ship HMS THAMES, but it is not known which submarines he may have served in. He then returned to general service, serving in the cruisers HMS BRILLIANT, BARHAM, PATROL, TERPSICHORE and ACHILLES.  In December 1909 he completed 12 years service from age 18 (as claimed), and joined the Royal Fleet Reserve.

Returning to Downton, William was recorded in 1911 living with his widowed father, age 72, both noted as Agricultural Labourers.

In May 1912 he rejoined the RN, signing on to complete a 22 year pensionable engagement. He was first drafted to the battleship HMS BULWARK and then, in May 1913, to HMS MAIDSTONE, the principal depot ship of the 8th Submarine Flotilla. On the outbreak of war, MAIDSTONE led her Flotilla to its war station at Harwich.

William Mitchell died in an unusual accident on Saturday 13 March 1915. He was attending a concert being given to RN personnel at Parkeston Quay, when a gallery in the hall collapsed suddenly. Mitchell was the only man killed, but an Engine Room Artificer from MAIDSTONE was also seriously injured and a number of others received minor injuries.

He is buried at Shotley (St Mary) Churchyard – RN Plot 31.