This month's image has been selected to mark the publication of my latest book – The Governor – controlling the power of steam machines was published in hardback by Pen & Sword books on 11 November. The research and photography for the book took me all around the country over a two year journey of discovery and introduced me to some amazing machines – and to some fascinating people who generously shared their knowledge with me. This photograph was taken at Coleham Pumping Station in Shrewsbury and shows one of their pair of 1899-built Woolf-type rotative beam engines in steam. The engines were built by W. R Renshaw of Stoke-on-Trent and are governed by two centre-weighted Porter Governors. Charles Porter had patented his design more than forty years earlier, on July 13, 1858, and it was one of the earliest weighted flyball governors. Taken with a Canon 5D MkIV and 24mm lens.