I've mentioned here before that my GF had a birth certificate which he believed to be his, and which as far as I have been able to tell, he obtained from Somerset House in 1946. However it was for a different person born the same year and having the same name. He died still believing it to be correct, and it set me on a merry goose chase when I first started my research, because I took it at face value and it was many months and a lot of research later when I discovered information that brought it into question.
He was orphaned at 3 years of age in 1901, taken into the care of the local poor law union, later placed on a training ship and went on to join the navy, so knew nothing of his actual parents or his family. But believing he was born in London (he wasn't, but his parents moved back there when he was only a few months old) having applied to Somerset House and given them his name, year and place of birth as London, the certificate he obtained was the only one they could have realistically come up with.