Martyn Johnson was born at Darfield, the son of a coal miner. Leaving school at the age of fifteen, his first job was as a blacksmith. His work changed dramatically four years later when he joined the Sheffield City Police Force where he served as a 'beat bobby' until 1969. A two-year spell in CID followed but, missing grassroots policing, he returned to the beat for a further seven years. Passionate about local history, Martyn is a well-known metal detector and has appeared on many BBC Radio Sheffield programmes talking about his hobby.
A long-time resident of Wentworth village, he also assisted and advised Catherine Bailey when she was researching her best selling book, Black Diamonds.