‘Is it going to be the Doctor’s defence that he improves?’ This is the segment of the trial that nearly everyone says works as a standalone story as if that’s a compliment. The court room scenes show some effort to address Peri’s death (more, in fact, than Adric got in Time-Flight), and to provide a bit of juicy context (this is an adventure plucked from the Doctor’s post-trial future, an idea that doesn’t bear more than half a second’s scrutiny), then it’s straight into the web of mayhem and intrigue aboard the very Season 17-looking Hyperion III.

It’s immediately obvious (if the Doctor’s melodramatic voice over hasn’t already made clear) that this is an Agatha Christie pastiche. The instantly hateable Professor Lasky mixes up a nine and a six; doddery old Kimber recognises another passenger who grumpily denies he is who Kimber thinks (and then turns up murdered), and Lasky’s colleagues react with alarm when they suspect an investigator is aboard. By the time the Doctor talks about ‘grey cells’ even the half-watching dads must have got it.

It’s a good concept, and this works well as an opening episode, with the Doctor, like Poirot, already familiar to the long-suffering Commodore Travers, and a resentful local “policeman” in Rudge, and a clear focus for the shady activity (the mysterious seeds and pods in the cargo hold). It’s a bit let down by the design of the luxury liner, which looks more like a cross-channel ferry (the cabin scenes could be from an episode of Triangle), but at least the intent is clear.

I’m slightly less sold on ‘Melanie known as Mel’. I like Bonnie Langford, who brings some welcome enthusiasm back to space and time travel (pretty much all the earlier JNT companions seemed to barely tolerate it), but I’m unconvinced abut her lack of an “origin story”. Other than the character brief (a 1980s computer whizz from Pease Pottage), there’s not much that suggests contemporary woman, and with minimal effort she could have been one of the passengers, perhaps one who takes a shine to the Doctor and muscles in on his investigation – while being a suspect herself (and getting some backstory). What we actually get is a fitness fanatic who gently bosses the Doctor to lose weight (bit mean) instead of complaining at him. Still, a companion who wants to travel with the Doctor, and a straightforward return to adventuring isn’t a bad thing at this point. And she does do a great cliffhanger scream.

Next episode: The Trial of a Time Lord – Part Ten