he became well known within the series for a number of instances, one being a stunt in which he performed an (unpaid) back flip when he "died" in "the sea devils". he also had to stand in for kevin lindsay in "the sontaran experiment" when lindsay's heart condition made it too difficult for him to complete his lengthy fight scene. another notable instance was in "the invasion of time", in which he improvised a jump (in full costume) and almost fell down as he landed on a folding chair. he then fell over a chair thrown at him to only narrowly stop himself from rolling into location's swimming pool. the whole sequence ended up being used in the final version. stuart fell explained, in a 2004 documentary, that he was encouraged to improvise and the it was felt that these trips made the scenes more interesting.