Thanks for all your replies.
The newspaper articles looked interesting. I went further back in time and found one in the Islington Gazette dated 12 Jul 1888, where they mention a name, Police Constable Stephen Chapman 61 G.
I've found a family tree for a Stephen Edward Chapman, born 1860 Bermondsey, on Ancestry, which includes a photo in later years. Unfortunately his features do not resemble those in my photos and his family tree does not include any names I'm familiar with.
I've found a record in the National Archives Discovery which gives his dates of service in the Met from 20 Apr 1885 until 25 Apr 1910.
"Stephen E Chapman, warrant number 70563. Joined on 20 April 1885, and left on 25 April 1910. Last posted to G Division as a PC."
Maybe my PC 61 G joined after 1910.
I also do not recognize the name Alfred Ross, but I'll double check. Thanks again for all your help.