Popularized in folklore was Merlin the wizard who lived in a castle, were there actually any real well known alchemists that worked for kings?

by wizardomg
CChippy

Not quite the same question that you are asking, but close; John Dee, as mentioned in an earlier reply might meet your requirements.

https://www.reddit.com/r/AskHistorians/comments/1zvnbv/in_medieval_england_was_anybody_ever_employed_as/