The opening credits get a makeover

We won’t spoil the surprise but look out for some additions to the title sequence that will definitely get you in the festive mood.

There’s a special guest role for a Game of Thrones star

You won’t have seen his name in the cast list yet but keep your eyes – or should we say ears – open for an actor who once had dealings with Daenerys Targaryen (it didn’t end well for him).

And a throwaway reference to the Eleventh Doctor

Blink and you really will miss it but as River Song sorts through her bag in an early scene, we get a glimpse of an item that could feasibly have belonged to Matt Smith’s incarnation. Clue: it’s not a bow-tie but it is cool…

We get a brief glimpse of some other familiar faces

Just a dozen or so, and not for long, but you’ll definitely recognise them.

It’s Sonic City

We’ve already seen the Doctor’s new Sonic Screwdriver, and got a look at what we’re guessing is River’s Sonic Trowel, but one or two other Sonic items might just turn up before the episode is out.

A clue in River’s diary reveals where we are in her timeline

When River first meets the Twelfth Doctor she appears not to recognise him (something that irritates him no end). But when the final excerpt from her TARDIS diary is read out we realise when and where she last saw the Time Lord and which face he was wearing.

The Doctor gets jealous

Whether or not you’re sold on the chemistry between Peter Capaldi and Alex Kingston, it’s clear from the Doctor’s behavior that he’s a bit put out by her dalliances with other men and her refusal to acknowledge their past.

The Doctor gets political

Jeremy Corbyn would be proud as the Doctor embarks on a minor rant about the pointlessness and injustice of royalty.