Apologies I forgot to add in my last.

Someone mentioned choirs and their "scores" - In the only choir I ever sang in, we all knew the material, all knew our parts, the scores were carried simply in order that we had something to do with our hands (i.e. they were not moving about and causing a distraction - the choral director regarded that as being the job of his hands).

Les Barker does probably know his stuff off pretty well "by heart" but with his stage persona, the hand-held manuscript is used as a stage prop, and the deliberate pauses to consult it seem to have more to do with comic delivery and timing rather than for him to know what comes next.