RW Mills as Joseph in Nativity Play.jpg

I've found a mention of this in John Charter's diary, which shows R W Mills played Joseph in the Nativity play performed at Christmas, 1943. Charter is writing about the play 'Laburnum Grove' that he was producing:

Gordon Stopane-Thompson was playing the part of Detective Inspector Stack, but he was not well and developed boils and so I decided (very reluctantly) to understudy the part myself. Richard Mills - who was already rehearsing as Joseph in the Christmas Nativity play and as an ugly sister in the pantomime 'Cinderella' - offered to play the part if I did not want to do it myself.

Eric MacNider's diary notes the "C. of E. Nativity play" play on 24 & 27 Dec 1943.

Savitsky also painted R W Mills in those other two roles:

RW Mills as Inspector Stack in Laburnum Grove - 19431230.jpg, by AJ Savitsky

RW Mills as Edith in Cinderella - 19440119.jpg, by AJ Savitsky