Rome actress Lindsay Duncan is to guest star as Doctor Who's assistant in one of the upcoming BBC specials, it has been announced.
Duncan, 58, is to play Adelaide, reportedly the Time Lord's most intelligent and strong-minded companion yet.
Currently starring as Baroness Thatcher in BBC2 drama Margaret, Duncan studied at London's Central School of Speech and Drama and is a Tony award winner, for Tom Stoppard's Private Lives.
She will join David Tennant in the as-yet-untitled second Doctor Who special of 2009, one of his final four episodes before Matt Smith takes over.
"I'm thrilled to be involved in Doctor Who. I've never done anything like this before and I'm really looking forward to working with David Tennant and the Doctor Who team," she commented.
Russell T Davies, who is co-writing the second Doctor Who special, said he was delighted to announce Duncan's casting.
"Lindsay is an incredibly talented actress and I've been an admirer of her work for some time," Davies added.