I'm delighted to say that 2 years on I am able to share a success story identifying the mystery photo of the police officer in this post. After looking into my great great uncle's first marriage to a lady called Martha Evelyn Dunn, I discovered from the 1911 census that she was the only child of one Police Sergeant Henry Henderson Dunn, and that the family were living near Ulverston in the South Lakes. I started digging and got in touch with Lancashire Archives who, free of charge, were able to provide assistance to dig out the personnel file of a Henry Dunn who served with the Lancashire Constabulary from 1884 to 1912. From this file they were able to provide details including DOB, place of birth, marriage, and districts served that matched up with the man from the censuses. They also provided his Police Collar Number, and (wollah!), it matched the number in the photograph - 280, giving me the solid evidence needed to confirm the mystery officer. Thank you to those who pointed his collar number out to me as I may have never noticed it myself!
I also searched his name in the British Newspaper Archive and found an amazing article upon his retirement, portrait included, covering his service history and beginnings in Preston, shining a light on why he had his photograph taken there. His daughter and my great great uncle didn't have any children of their own which explains why the photo has come to be in my possession.
I would recommend to anyone interested in researching people who served with the Lancashire Police Constabulary to use the Lancashire Archive search facility (
https://policesearch.lancashire.gov.uk/policesearch.asp). Amazingly they have photographs of new recruits pasted in the Examination Books between the years 1875-1878 and 1885-1886, and then from 1886 in special Photograph Books.
