Hello everyone from the sweltering heat of Dubai,
Thank you all for your replies and interest.
I just wanted to clarify that I am asking about the likelihood of a man swapping his given name and his family name.
The 1812 marriage recorded in the register of London's Great Synagogue indicates that the groom's given name was Hyam in English and Chayim in Hebrew. His English family name was apparently MOSES.
Is it likely that that he later chose to call himself Moses (given name) HYAM (family name) for civil purposes, i.e. change his family name?
Were the family names used by the Jews of early 19th England fixed or was there a degree of fluidity?