John Farwell was born in Peshawar, Bengal, India (now in Pakistan) on 12 December 1891, the eldest son of Lt Colonel Walter Charles Farwell, Bengal Army, and Margaret Mary May Farwell (née Lomond). He joined the Royal Navy as a Cadet on 15 September 1904. He was promoted to Midshipman on 15 May 1909 and was appointed to the battleship HMS BELLEROPHON on the same date. John Farwell served in the cruiser HMS INVINCIBLE from 11 October 1910 to 10 January 1911 and then joined the cruiser HMS ACHILLIES on 14 January 1911. From 15 May 1911 to 13 May 1912, he served in the battleship HMS St. VINCENT before joining the Torpedo Boat Destroyer HMS CHELMER on 18 June 1912. He was promoted to Sub Lieutenant on 30 August 1912 and, in October 1913 he was appointed to the battleship HMS TRIUMPH. John Farwell was further promoted to Lieutenant on 30 August 1914 and, on 11 May 1914 he joined the cruiser HMS YARMOUTH.

He joined submarines when he was appointed to the Submarine Depot Ship HMS BONAVENTURE ‘for Submarines‘ on 22 December 1914 and to HMS C16 as First Lieutenant to date 8 April 1915, followed by HMS D6 as First Lieutenant to date 31 August 1915. His next appointment was to HMS E30 as First Lieutenant on 10 February 1916. E30 was presumed to have been lost with all hands in a previously unknown minefield off of Orford Ness on 22 November 1916.

John Farwell is commemorated on the Portsmouth Naval Memorial on Panel No 11 and his name is recorded on the Cheltenham Roll of Honour.