Just to add to any possible confusion.
In the UK one can change their name by a number of means, one of which is Common Law, which does not require any legal action i.e. solicitor, declaration etc.
That means, providing I am not changing my name for a dishonest purpose, I can change my name to almost anything I wish, as long as I don't include a name which implies a tile e.g. Lord John Smith, but I could change it to John Lord. All I need do is tell everyone I have changed my name. To get a passport amended or issued in the new name requires a statement from the category of person who can countersign an application, to the effect that they have known you for x number of years and as of ..... date.... you have changed your to ........
About 25 years ago in UK I changed my first name and surname and got a new passport in my new name which has no reference to my birth name.
As for changing names on marriage, that is a practice and not a legal requirement. If Mary Smith marries John Jones, she can remain Mary Smith, or change it to Mary Smith Jones or Mary Jones, or anything else.
My wife wanted to use my surname. We live in Spain where it is custom for a woman not to change her name on marriage, however, we went to Philippines Consul and amended her passport so now it shows she is Mrs Elaine Smith Jones.
