A quick search using 'comic' or 'home defence' with 'Sopwith Camel' yielded a few sites where this was stated - GreatWar Forum has a thread where
multiple posters agreed the engine was a LeRhone, and a blog by Christopher Chant (cmchant.com), "Sopwith Camel - another classic British fighter of WW1", 20/06/2011, definitely states that comic Camels had a LeRhone 9J engine.
I don't know how definitive this is, but there seems to be a consensus.