Online trees have him as Leonard Arthur Spencer, born on 18th November 1921.
Mother's surname was Seaman, as in the GRO. She is wih Arthur J in 1921
The Arthur J Spencer in Ealing, in 1939, matches the birth date in the trees.
He married again to Kate Borrowman, who is with him on the register.
Winifred married again to Ernest W Fleming, and they are together in 1939.
No sign of Leonard Arthur, so probably in the services, as K Garrard mentioned.
David
Thank you that would make sense it seems he did serve in the army. I wasnt aware that winifred also remarried. So i will look into that further.