Llewellyn's involvement with Red Dwarf came about as a result of his appearance at the Edinburgh Festival Fringe, performing in his comedy, Mammon, Robot Born of Woman; this show was about a robot who, as he becomes more human, begins to behave increasingly badly.
Llewellyn joined the cast of Red Dwarf in 1989 in series 3 and has continued in the role up to 2016's eleventh series.