Blood Grouping.

Was watching Series 1 last night. No DNA fingerprinting in those days and Blood Groups were used to decide on paternity. It proved very little, only if somebody "might" be father or "might not". It was very vague.
BSM Williams could have easily been Parky's dad. After all we would also need to know Edith's blood group.
Parky is "O" and that is recessive. BSM is AB, so he could easily be Parky's dad if he and Edith both carried the recessive gene. Or Edith might have been "O" and BSM williams carried the recessive gene. In that case Parky would have been "O", which he was.
My mother was "AB" and my dad was "O" but I am "B". Doesn't mean that my dad is not my father. It just means that with the very simple testing they did in those days, that he might not have been my father. they just would not have known. I get my blood group from my mother.
"O" is the commonest blood group in the UK and recessive.
I REALLY BELIEVE HE WAS PARKY'S DAD. THEY ARE VERY ALIKE IN MANY WAYS.IT WOULD HAVE BEEN NICE TO THINK SO.