I am going to suggest Rodney Bewes.
A few weeks back there was an episode of Masterchef where the contestents made afternoon tea for some veterens of TV comedy. There were a number of people who had featured on this site such as Frank Thornton as well as Nicholas Smith (Mr Rumbold), Lynda Baron, Wendy Craig and Jeffrey Holland but it took me several minutes to recognise Rodney Bewes and even my wife commented that she expected to hear of his death shortly.
Bearing in mind I think the series was filmed at the end of last year I am not even sure if he will make 2013.
I tried to add a photo but I am having to post as a guest as my account has not yet been validated.
I have already made this comment in the Basil Brush thread but thought it was a bit obscure!