Henry Dench Mayne was born in Fishbourne, Sussex, on 8 December 1875, the son of Henry and Elizabeth Mayne.  It appears that when he joined the Royal Navy his date of birth was recorded as 8 December 1876.

Henry Mayne served as a submariner from 8 December 1906 to 22 September 1908 and from 14 November 1911 to 25 July 1915 in submarines HMS E9 & E11. He served in HMS E11 at the Dardanelles and was on board for that submarine’s first patrol in the Sea of Marmora, during which he was awarded the Distinguished Service Medal (DSM) – see London Gazette dated 13 September 1915 – for his services in E11 at the Dardanelles and in the Sea of Marmora.

He was accidentally lost overboard in the Mediterranean about 150 miles from Malta on 20 July 1915. HMS E11’s First Lieutenant, Lieutenant Guy D’Oyly-Hughes (q.v), jumped in to save him but Mayne was lost. D’Oyly-Hughes was awarded the Silver Medal of the Royal Humane Society in 1915 for his efforts to save Mayne.

He left a widow Elizabeth Jane Mayne of Ingleside Cottage, Old Fishbourne, Chichester, Sussex.

Henry Mayne is commemorated on the Portsmouth Naval War Memorial, Panel No. 8.