 In planning the climactic chase in which Doyle pursues Charnier  across Marseilles, director John Frankenheimer (qv) wasnt aware  that Gene Hackman (qv) suffered from knee problems. Despite this,  Hackman went ahead and filmed the entire chase without a double,  badly inflaming his knee by the time he was through. He has said  that Doyles expressions of pain and determination as the chase  progressed didnt require much acting.