Peter Tuddenham voiced the on board computers Zen (of the Liberator) and Slave (of Scorpio) and took over from Derek Farr as the voice of the supercomputer Orac. Given his talents, it is perhaps surprising that he only performed in three televised Doctor Who stories during his career. His dulcet tones can be heard in The Ark In Space, The Masque OF Mandragora and Time and the Rani.