John Wilkes is an Australian who believes that Sauniere discovered lost treasure in a cave hidden somewhere beneath the Rennes-le-Château area. He carries a seismic survey machine that becomes the butt of ridicule for Gabriel. Wilkes himself appears arrogant at times and constantly tries to hit on Madeline, with little success. He later turns his interests towards Grace, who plays along in order to discover Wilkes' findings. He has a musculine built and a prominent moustache.
He, in fact, discovers the temple and its entrance and is killed by Montreaux's lackeys as a consequence. His discoveries do help Grace in her investigation.
Personality and traits
Wilkes is an Australian of the exceedingly macho variety. In his late 40's, Wilkes has been all around the world -- at least the desolate parts of it. He's a real treasure hunter, that's quite obvious (although he won't talk about it unless exceedingly drunk or well-seduced). Wilkes believes he has the secret of the treasure of Rennes-le-Chateau. He believes the secret will make him incredibly wealthy. But he ought to be careful to whom -- and how loudly -- he brags about it.