We have good news for Doctor Who fans. Some very good news.

Because instead of having to wait until Christmas for the next sighting of the Time Lord on TV, it’s going to come rather sooner than that. Next month, in fact.

Peter Capaldi’s Doctor is to guest star in the opening episode of Class, the scary sci-fi spin-off destined for BBC3 in October.

It is set to be repeated on BBC1, giving fans a chance to see him in action way ahead of his scheduled re-appearance in the festive special.

In the plot, written by Patrick Ness, four Coal Hill School sixth formers have all the normal teenage problems involving friends, parents, school work and sex – but they also find themselves facing the end of existence.

They are kept in line by their teacher, played by ex-Corrie favourite Katherine­ Kelly . One insider said: “What sort of trouble must those kids get themselves in if they need the Doctor to come and bail them out?”

Doctor Who showrunner Steven Moffat has promised Class will be like “a British Buffy”, saying it would be “dark and sexy and right now”.

We hear there have been a few tweaks along the way, as BBC bosses struggled with their edgy show’s, er, edginess.

Certain scenes have even been re-shot in a bid to improve the final offering. But a gay sex scene between one of the teenage characters and his older lover remains intact in the third episode, we’re assured.

There had been rumours that the scene in the drama, largely set in Coal Hill School, caused particular concern.

Despite being aimed at young adults like previous spin-off Torchwood, BBC chiefs worried that Capaldi’s appearance would attract young kids to tune in.

Writer Ness is clearly thrilled with how the series has turned out. “I put my heart into it,” he tweeted at the weekend as filming wrapped. “Can’t wait for you to see it.”

As there is no Doctor Who series this year, let’s hope Class can keep fans happy for the time being, until he pops up in the TARDIS again next year.