Sorry, you’re wrong. Marriage had nothing to do with it. All a father had to be was a Citizen in good standing of the UKC.
Absolutely Incontrovertibility Incorrect.
Marriage had EVERYTHING to do with citizenship law for persons born outside of Britain.
As a matter of fact, even here in the US marriage has also played a part in citizenship as seen in the Nguyen case.
You can believe it or not believe it. All one need to is actually read the law you cited.