I have one born under one surname - that of his mother. His mother soon afterwards married, and when this youngster started work, he was surprised, to say the least, that the surname his foreman addressed him by was that of his mother, not that of her husband and his two siblings, that he'd used until then. He adopted that family surname, and later served in WWII, married, worked and died under that surname ... but no evidence of a formal deed poll taking place, although we've looked for it. It happened a lot.