No, he wouldn't have had to do it officially, he could have just quietly gone ahead and done it; this is quite legal so long as fraud isn't involved, and after 1916 so long as he was not an alien. There are several ways which would be recorded: (1) advertising in a newspaper; (2) a private act of parliament; (3) a royal licence, normally advertised in the London Gazette; (4) by deed poll, accompanied by enrolment in the Close Rolls of Chancery (until 1903) and later in the Enrolment Books of the Supreme Court. Look at the article on surnames in Terrick FitzHugh's 'The Dictionary of Genealogy'; a free leaflet on 'Change of Name' s available at the PRO. Regards, Colin Mills