Peter Capaldi’s regeneration into the next Doctor will be “like no other” say show insiders.

The moment when the Twelfth Doctor hands over to the Thirteenth is of course still shrouded in secrecy but the indications are that Capaldi will go out in style.

“Just because we have done it one way in the past doesn’t mean we will do it the same way again – in fact you can definitely expect the unexpected when the time comes,” said a senior source on the show.

Speculation is of course rife about who Capaldi's successor will be – with Kris Marshall, Sacha Dhawan and Phoebe Waller-Bridge all thought to be in the frame – but the manner and the timing of his departure has also got fans guessing.

Will he be replaced in the Christmas special which follows the current series? Or will he regenerate mid-series in a surprise move?

Capaldi's final scenes are expected to be filmed in the summer for a likely handover during the Christmas special which marks Moffat’s last episode of the drama.

Last month Capaldi himself claimed that the pivotal scene has already been shot – and that the Twelfth incarnation “goes out a fighter”. 

"I did [the regeneration] the other day," Capaldi told the Sydney Morning Herald. "It was a strange day. It was explosive. He goes out a fighter."

Capaldi may be referring to the regeneration scene already glimpsed in the below trailer, which most fans believe to be a "fake-out" in the vein of similar halted regenerations for David Tennant and Matt Smith’s former Doctors.

One theory is that Capaldi’s Doctor will begin to regenerate this series only for the process to be stopped for some reason. It will then be completed in the Christmas special when he transforms into incoming showrunner Chris Chibnall's new Doctor, the suggestion goes. 

Chibnall has already started pre-production on the show and is currently talking to writers and sketching out ideas for his series arc when he starts, add sources.

His tenure is expected to begin when he writes the final scene of the Christmas special and begins in earnest with series 11 which will film next year for a possible broadcast in Autumn 2018.

As for who will actually land the new role, well-placed BBC drama sources suggest that a decision has still not been made.

"The new Doctor has to be approved by the top brass but ultimately it is the choice of Chris Chibnall and [incoming executive producer] Matt Strevens because the new Doctor has to work with them.

"Of course if they choose their gran for the role questions must be asked but ultimately the decision is theirs."

Doctor Who is on BBC1 on Saturday nights