Complex sentence: Despite never reprising his role as Q, Burton did however make two uncredited reappearances in Bond movies, first as an RAF officer in "Thunderball" (1965), and later as a secret agent in the satirical "Casino Royale".
Split into simpler sentences: Despite never reprising his role as Q, Burton did however make two uncredited reappearances in Bond movies. First as an RAF officer in "Thunderball" (1965), and second as a secret agent in the satirical "Casino Royale".