David Ross (born in 1945, in Blackburn, Lancashire) is an English actor who has worked in theatre, cinema, and television. He played the character Kryten in the Series II episode of the same name but was replaced by Robert Llewellyn for all later depictions.
He again appeared in the Series IV episode "White Hole" as Talkie Toaster, reprising John Lenahan's role from Series I as a cameo. He then reprised the role of his own cameo for the Series XII episode "Mechocracy".
According to the audio commentaries, the main cast were left with the impression he placed a high value on actors being 'legit', in other words (presumably) grounded in the theatre.