The following was found on a UK website and deals with copyright photographs taken in the UK:
https://www.copyrightaid.co.uk/forum/viewtopic.php?f=3&t=2312
Post by AndyJ » Tue Mar 06, 2018 4:28 pm
Hi rmlaws,
You are free to use the photograph as you wish. Firstly, under the 1911 Copyright Act, all photographs whether published or not, had a fixed copyright term of 50 years from the date they were made (ie the photograph was taken). Hence copyright in your particular photograph would have ended on 31 December 1951.
Furthermore, another provision in the same Act (section 5(a)), said that where a person commissioned the taking of the photograph, that person would be the owner of the resulting copyright unless there was some express provision to the contrary. Thus in all probability, one of your family members who paid for the sitting will have owned the copyright, which by the normal laws of inheritance would have passed down through to his or her heirs, until it expired in 1952..