Doctor Who’s series finale sees the return of one of the Time Lord’s most-feared enemies and is “massively game-changing”, the show’s writer has said.

Jodie Whittaker returns as the titular time-traveller to close out her second series in the role and will be up against an army of Cybermen.

Set in the far distant future, the two-part episode sees the Doctor tasked with helping a rag-tag group of human refugees trying to escape the Cybermen determined to wipe out what is left of humanity.

Doctor Who
Jodie Whittaker’s second season as the Doctor will come to a climax this weekend (Ian West/PA)

Writer Chris Chibnall promised the finale will be “massively game-changing”, adding: “I’m really looking forward to watching the final two parts go out because we’ve still got something up our sleeves!”

The series 12 finale, titled Ascension Of The Cybermen, will also provide more details on the mysterious new version of the Doctor played by Jo Martin.

Martin emerged as a predecessor to Whittaker’s iteration of the believed character, but details of her murky past have been few and far between.

Some of those questions will be answered in the finale, Chibnall said.

“I think viewers would be right to hope for that,” he said.

“Obviously it goes back to episodes one and two with Sacha Dhawan’s Master telling the Doctor that everything she knows is a lie.

“As we come into the final two-parter we will learn much more about what that means for the Doctor.”

Doctor Who continues on BBC One at 7.10pm on Sunday.