It's possible that:
* The name is misspelled: Perhaps you're thinking of a different author with a similar name.
* They're not a well-known author: There are many talented writers who haven't achieved widespread fame.
* They're not a published author: They might write for personal enjoyment or for a specific niche.
If you have any more details about Tony Mitton, such as their genre, books they've written, or any other identifying information, I might be able to help you find more information.