Apparently:
"Actor Sir Derek Jacobi is set to appear as an extra in Coronation Street, it has been revealed.
The stage and screen star was on a private visit to the soap's Manchester set and was filmed at the back of a shot in the Rovers Return pub.
It is likely that viewers of the ITV1 drama will not spot Sir Derek, who is best known for his Shakespearian roles."
Blink and you'll miss it.
http://www.bbc.co.uk/news/entertainment-arts-17675806