The John Noble who appears on the Legends of Tomorrow episode — which is perfectly titled as “Guest Starring John Noble” — will apparently be John Noble circa the filming of The Two Towers and Return of the King.
Of course, even Legends of Tomorrow isn’t crazy enough to pretend that the Lord of the Rings trilogy is based on a true story and Denethor’s real name has been John Noble all along.
Obviously this one photo isn’t enough to say much about the John Noble of Legends of Tomorrow, but he certainly looks like a goofier guy than Denethor II.
The shot of Noble on Legends of Tomorrow places him in a trailer, smiling in a most un-Denethor way, and chatting with what seems to be Ray pretending to be a production assistant.