A UK passport has a "surname" field and a "given names" field. But a recent UK birth certificate has a single name field in which the "surname" part is distinguished by being written in capitals, so "Peter James ADAM SMITH" would have a surname consisting of two words. But what if a word consists of a single letter? For example, some Irish surnames look like "O Briain", and I think there is a Vietnamese name that consists of a single vowel, so presumably you can't always tell from the birth certificate which part is the surname.
A UK passport has a "surname" field and a "given names" field. But a recent UK birth certificate has a single name field in which the "surname" part is distinguished by being written in capitals, so "Peter James ADAM SMITH" would have a surname consisting of two words. But what if a word consists of a single letter? For example, some Irish surnames look like "O Briain", and I think there is a Vietnamese name that consists of a single vowel, so presumably you can't always tell from the birth certificate which part is the surname.