Matt Smith impressed soprano Katherine Jenkins by singing to her between takes on the set of the Doctor Who Christmas special.
The Welsh soprano, who plays the part of Abigail in the drama's festive outing, reckons the actor has great vocals.
She said: "I had a really good laugh with Matt between takes. He kept mucking around and singing to me but, you know, people should hear him - I think he's got a great bass voice!"
The blonde had doubts about trying her hand at acting, but couldn't turn down the chance to be in Doctor Who, which is filmed in her native Wales.
"I'd been asked to do things in the past and hadn't done them, but when I got the call to do Doctor Who, it really excited me. It's such an iconic show and one we all watch as a family.
"I wasn't sure I could do it but after reading for the part, I got a call on my 30th birthday to say I'd got it. It was the best birthday present I could have asked for!"
Viewers will also hear her Katherine sing in the show, Doctor Who: A Christmas Carol, which is broadcast today on BBC One.
Matt, who plays the Time Lord, added: "Katherine looks like a princess, and boy can she sing - the way she controls her voice and the grace with which she sings is quite incredible. It's exactly the type of casting we want - someone fresh, exciting and new."