Stephen Fry has begun filming scenes for the new Doctor Who series – where he will appear as a special guest.
Timelord Jodie Whittaker has been pictured by fans filming in Swansea over the last few days.
And several said they had seen Fry, 61, in a tweed 40s style suit on set. A Tardis was also spotted being used in Swansea's Guildhall.
A source on the show confirmed Fry was one of the guest stars appearing in the new series, which will not air on BBC1 until 2020.
Fry is known to be a Doctor Who fan and has appeared in a number of other BBC shows over the years including Blackadder, A Bit of Fry & Laurie and travel series Stephen Fry in America.
In December, Doctor Who showrunner Chris Chibnall admitted Series 12 would not start until 2020 even though they had begun work on it.
At the time he said: “We're off again! Well we never actually stopped.
“As Jodie Whittaker's Doctor and friends have been winning the hearts of families across the nation this autumn, we've been busy with a whole new set of action-packed adventures for the 13th Doctor.”
He added they couldn't wait to bring "more scares, more monsters and more Bradley Walsh, Mandip Gill and Tosin Cole" - referring to the Doctor's companions.