The 30-year-old actress, who plays Bill Potts, admitted that she couldn’t help but cry over the emotional script.

Speaking to press including express.co.uk at last night’s premiere of Twice Upon A Time, Pearl teased: “I was a state [reading the script].

“I was warning everyone I spoke to to bring tissues when they saw it because it’s quite an emotional episode.”

David Bradley, who plays the first Doctor in the thrilling episode, echoed Pearl’s sentiment. 

The 75-year-old gushed: “I’m a little overwhelmed watching it tonight. 

“I thought, ‘I’m in this!’” he laughed.

Although details of the highly-anticipated episode are being kept under tight wraps, fans can guarantee that the twelfth Doctor’s regeneration is sure to be a tear-jerker.

The Captain actor, Mark Gatiss, added: “It’s such an emotional thing to watch, I was in pieces. 

“It made my heart sing, it was beautiful,” the 51-year-old explained.

The synopsis teases: “The magical chapter of the Twelfth Doctor’s journey sees the Time Lord team up with his former self, the first ever Doctor and a returning Bill Potts, for one last adventure.

“Two Doctors stranded in an Arctic snowscape, refusing to face regeneration. Enchanted glass people, stealing their victims from frozen time. And a World War One captain destined to die on the battlefield, but taken from the trenches to play his part in the Doctor’s story.

“An uplifting new tale about the power of hope in humanity’s darkest hours, Twice Upon A Time marks the end of an era. But as the Doctor must face his past to decide his future, his journey is only just beginning…”

As well as this, the episode will see Peter’s regeneration into incoming Time Lord, Jodie Whittaker.

Doctor Who Christmas special airs on Christmas Day on BBC One at 5.30pm.