Pauline Collins, Anthony Head, Maureen Lipman, Roger Lloyd-Pack and Sophia Myles are also on board for the next series, the Guardian reported.
Executive producer Russell T. Davies said there is nothing funny about the role Kay is about to play.
"This is not a comedy turn," he said. "Peter is a versatile actor who has appeared in Paul Abbott's 'Butterfly Collectors' and 'The Secret Life of Michael Fry.'"
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