She was, indeed, an excellent actress. It was almost impossible to watch her portrayal of Alice and realise that you were actually looking at a highly-intelligent woman. The script alone created only a 'cardboard cut-out' comic figure; it was her perfect timing that turned that figure into a wholly-believable character.
My favourite moment was when she was reading from an 18th century bible. In the typography of those days the letter 's', unless at the end of a word, looked very much like an elongated 'f'. At the end of the programme she read the lesson and hit on the word 'succour'. She managed to say 'f' before the credits rolled and the theme tune played.