Hi Frank,
I agree with molar.
My daughter was born in Berlin, of british parents, living in Berlin, and is a british subject, with right of abode in the UK (says so in her passport !)
BUT: was he
... born a German subject and later took British nationality?
An interesting question ! As far as I know it has never arisen before, but it is possible.
After all, if he is proud of becoming british, then he may have stressed this, if the enumerator queried his german birthplace.
Looking forward to hearing other views on this .....