James Mardell was born in 1882 in Welwyn, the son of James and Ann Mardell. His father died in 1886 and on the 1891 and 1901 Censuses, he was living with his widowed mother and siblings at Welwyn Hill, Welwyn.
In 1901 he was working as a domestic gardener. He married Constance Maud Kirby in 1905 and by the 1911 Census, he was living at Digswell Water Lodge, Nr Welwyn with his wife, daughters Annie and Ada and his widowed mother-in-law, and working as a domestic gardener. They later had a further two daughters, Nellie and Grace.