Harold John Badcock was born on 28 February 1888 at Boxmoor, Hemel Hempstead, the son of Francis St John and Marian Badcock (nee Sparkes). He was one of six children and his father was the principal teacher at Boxmoor School.
On the 1891 Census the family were living at School House, St John's Road, Hemel Hempstead, where his father was a teacher at the Elementary School. His mother was also listed as a Teacher. They remained living at the School House in 1901 and Harold was then attending the school and his 18 year old brother Frank was also a teacher there.
His mother died in 1906 aged 49 and is buried in Heath Lane Cemetery, Hemel Hempstead.
By the 1911 Census Harold had moved out of the family home and was living as a boarder at the home of Alfred and Rose Wesley at 59 Cranwell Road, Lincoln and employed as a Police Constable for the County Constabulary. He later transferred to the King's Lynn Police Force and worked as Chief Clerk.
His father remained at Boxmoor School House in 1911, working as the Head Teacher, and Harold's siblings Percy, Elsie and Dorothy were living with him, along with servant Lily Hoar.
Harold married Hilda Gladys Frogley on 12 October 1915 at St Mary's Church, Hemel Hempstead. Her father was Superintendent of Police in Hemel Hempstead between 1892 and 1918. The wedding was reported in the Hemel Hempstead Gazette with a detailed description of the participants and description of the bride and bridesmaids' attire.
His father died in 1917 and is buried in Heath Lane Cemetery, Hemel Hempstead.