Hippie wigs in all 4 series..?

I watched Rising Damp series one and understood that Richard Beckinsale was wearing a wig because his other character in Porridge required him to have short hair; and it was filming at the same time as Rising Damp series one.

I just watched Rising Damp series three this past week. I noticed his hair was a bit shorter than the sries-one wig, but still long.
Was he wearing a wig in series three? or was it his natural hair by then?

I don't recall hearing that richard wore a wig at anytime.
in stage struck, he cuts his hair to ward of hilary, and it stays short afterwards, which would suggest it was his natural bonce?