 Mundin was born in St Helens, then in Lancashire (now part of Merseyside).His father was a nomadic, Primitive Methodist home missionary.His family moved within a short time of his birth to St Albans in Hertfordshire (the 1901 census data reveal that the family lived at St Helens Villa, Paxton Road, St Albans; his parents William and Jane apparently naming their house after the town where they first met and where Herbert was born).