It's possible that:
* The name is misspelled. Double-check the spelling and search for alternative spellings.
* The actor used a different name. Check the credits for "Children of Stone" for any actors who might have used a pseudonym or changed their name later.
* The show's cast lists are incomplete. Some online sources might not list every actor involved in the production.
To further investigate, you can try:
* Searching online for "Children of Stone" cast list.
* Checking the British Film Institute (BFI) website. They often have extensive information on UK films and television shows.
* Contacting the BBC archives. They may have more detailed information on the show's cast and crew.
Without more information, it's difficult to determine what happened to the actor you're looking for.