Maurice Joseph Micklewhite has changed his name. Big deal? Yes, because he has changed it to Michael Caine which is how the actor has been known for years. He is reported to have made the change "legally'. It was probably by deed poll.
Deed poll is the best way although, strictly, no document is needed. A snap of the fingers and a word in the ears of your friends is legally sufficient to effect a change. But, in practice, you will run into trouble with banks, building societies and the rest who will demand to see written evidence of the change before they will alter their records.
Be careful. Use of a name for any fraudulent purpose is outlawed. However, anyone cursed with an unspent criminal conviction or a bad debt black mark will not be breaking the law by a name change so long as they do not tell any porkies about their past, if asked.
I rather fancy Lord Gold for myself. I'm just off to book a table at the Ritz - if I can get in! Before I do, be careful about changing the name of a child who is under 18 on their behalf. The Family Court may become involved if there is a dispute between parents about how a child is to be known in future. The Court of Appeal recently gave the thumbs down to a twin girl being called Cyanide. Wonder why?