Re: Name changed in London before coming to US, searching for original name #names
To add to my above response: There was no restriction even after 1919 to informal name changes for non-aliens. That remains the case. In 2020 - it is completely normal and legal for anyone over the age of 16 to start using a new name at any time, and absolutely no registration is required, so long as they are not doing so for a fraudulent or illegal reason. It could be by a completely private Deed.
Using a formal mechanism registered by the state (a Deed Poll) is and remains entirely optional.