Thanks. I must ask my friend if he has a copy of the marriage certificate or if his daughter perhaps has a copy as she had hired someone (presumably a professional geneologist) to research the family, with it seems little success. My friend's notes that he gave me advise that his birth father was a house factor, so perhaps someone did obtain a copy of the marriage certificate. The date of the marriage is on the birth certificate although the marriage took place after the birth, which was registered after the marriage.
The mystery is still, that his birth parents disappeared and no research has come up with any results.