The photo is of DD Snr on leave sometime during or just after training. I know he was born in Feb 36 and joined as a boy entrant so this would date the photo at about 52/53. He went through Yatesbury and Cosford.
What’s troubling me is what are the badges, why is the single strip upside down, and am I seeing things when I see a slight chequered cap band or is it a trick of the photo/light?