Mystery loco this time - probably a L&Y 0-6-0 at Hereford

Yes!

From Casserley & Asher, 'Locomotives of British Railways' Spring Books, 1961. There are two photos on P 323 a very similar loco.

The cutaway cab, the circular window, the 'mud guards' shapes, the steps between the lead and centre drivers, the handrail across the smoke box and number placement, the reversing bar, the funnel, and the rolled-over edge of the tender all match. The smoke/steam prevents me from seeing whether your Dad's photo has a belpaire boiler. I suspect it wold have been as the round top boiler seems to have a shorter fatter funnel.

The locos in the book are ex L&YR. Number ranges are 52088-52467 and 52515-52529. Back on P 68 it says 'Aspinall's standard L&YR 0-6-0 built in large numbers between 1889 and 1917. There were 246 survivors in 1948 and 70 still running early in 1960. No. 52322 has been restored under private ownership as L&YR No. 1122.'

Also a couple of pages about the class
en.wikipedia.org/wiki/L%26YR_Class_27
commons.wikimedia.org/wiki/Category:L%26YR_Class_27_1300

Hope this helps.

Thanks for your research, Graham. Looking at 52095 on Wiki it does look almost identical. I think that the boiler in Dad's photo may be round topped, but I don't think that the chimneys are that different. I have got his loco spotting logs but it could take quite a while to plough through them to see if I could link up the photo with an entry there.