Pearl Mackie has officially confirmed her exit from Doctor Who, and it’s a huge loss. By playing Bill Potts as an actual person – a questioning, clever, funny viewer analogue who was seduced by the Doctor’s responsibilities as much as his power – Mackie had the potential to be one of the all-time great companions.

But now she is no more. After the Christmas special, everything will change. And while Chris Chibnall might see Potts as surplus to the requirements of his new vision, he’ll hopefully be able to take plenty from her. Using her, and others, as an example, here are all the qualities he should be looking to bring to her replacement companion.

Confusion

Imagine that your mediocre, humdrum life is one day interrupted by a blazing god-figure who materialises from nowhere in a box. They’re in a hurry and they need your help, and in return they can show you everything that has ever happened and will ever happen anywhere in the universe. You accept their offer – of course you do – but you haven’t got a clue what’s happening, or what any of these monsters are, or 90% of what this stranger is telling you. Everything has to be explained. This is why the best companions function as a way into the heavy sci-fi of Doctor Who. If anything, Bill Potts leaned too heavily into this initially – her first handful of episodes largely consisted of her going “What’s that?” again and again – but her naivety was the perfect in for new viewers who’d otherwise be repelled by the dense mythology. With a new showrunner telling a new story with a new Doctor with a new gender, there’s going to be a lot of explaining to do. It would help if Jodie Whittaker’s companion was slow on the uptake.

Unsexiness

A legion of Doctors have tongue-slapped their way across the galaxy … including Matt Smith, who got off with his own Tardis. Photograph: BBC/Adrian Rogers/BBC

A few years ago, Doctor Who became an unrepentant snogfest, and it was weird. Ever since Paul McGann kissed Daphne Ashbrook 21 years ago, a legion of successive Doctors have tongue-slapped their way across the galaxy like a series of horny chimps. The nadir of this period was probably when Matt Smith got off with his own Tardis, but barely a companion made it out ungroped. Even Donna Noble, famed for her platonic relationship with the Doctor, ended up kissing him. Fortunately, the appointments of the Twelfth Doctor (too old) and Bill Potts (too gay) put an end to this, and hopefully it won’t restart in the Chibnall era. He’s already created one of the best cross-gender business-only partnerships in Broadchurch’s Hardy and Miller, so hopefully he won’t succumb to schlocky romance too quickly.

Humanity

Sure, if you’re an all-powerful alien with the power of near-eternal life, it’d be silly to only pick companions from a 50-year period on Earth, but that’s what the Doctor seems to favour. To be fair, that’s for good reason. Look at the alien idiots he has picked up along the way – Kamelion was wet around the ears, Romanadvoratrelundar was pointlessly aloof and Adric had absolutely no redeeming qualities whatsoever – and you’ll see what a better all-round choice humans are. In fact, the only truly successful alien companion has been Leela, and she loses points for being a nearly-naked humanoid savage who was only really there to keep the dads interested.

Endurance

Doctors don’t really stick around for long these days. David Tennant notched up 50 credited appearances as the Doctor, Matt Smith managed 46, and Peter Capaldi will just about scrape 40. Those aren’t particularly long hauls, and yet none have managed to find companions willing to last the course. Clara ducked out before Capaldi, Amy ducked out before Smith and, although they weren’t all primary companions, Wikipedia lists 12 separate pals for Tennant. It’d be terrific, and unexpected, if Chibnall was able to create a true partnership between Doctor and companion this time around; both sharing the full sweep of every episode from first to last.

So there: Doctor Who needs a stupid, unsexy human companion with nothing better to do. Suddenly those Kris Marshall rumours are starting to make a bit more sense. But perhaps a female-male dynamic is too old hat now. Maybe we need to return to the Jamie McCrimmon days and have a Doctor and companion of the same gender. What do you think? Young? Old? Male? Female? Human? Leave your comments below.