Alex Kingston is to reprise the role of River Song for this year's 'Doctor Who' Christmas special.

Alex Kingston as River Song

Alex Kingston as River Song

The 52-year-old actress has starred as the Doctor's wife in 15 episodes to date, starting in 2008 in 'Silence in the Library' and 'Forest of the Dead', and is set to meet her husband's new incarnation, Twelfth Doctor Peter Capaldi, for the first time on Christmas Day.

Alex - whose on-screen character is the daughter of the Doctor's earlier companions Amy Pond and Rory Williams - said: "To be honest, I did not know whether River would ever return to the show, but here she is, back with the Doctor for the Christmas special."

The actress also offered an insight into the much-anticipated episode, revealing scriptwriter Steven Moffat has created a typically humorous storyline.

She shared: "Steven is on glittering form, giving us an episode filled with humour and surprise guest castings.

"I met Peter for the first time at Monday's read through, we had a laugh, and I am now excited and ready to start filming with him and the 'Doctor Who' team. Christmas in September? Why not!"

Meanwhile, Steven said the return of River Song will ensure the Christmas special is an episode to remember.

He explained: "Another Christmas, another special for 'Doctor Who' - and what could be more special than the return of Alex Kingston as Professor River Song?

"The last time the Doctor saw her she was a ghost. The first time he met her, she died. So how can he be seeing her again? As ever, with the most complicated relationship in the universe, it's a matter of time."

Further announcements regarding the episode's cast - which also includes Jenna Coleman in the role of Clara Oswald - will be made in the coming months.