I really like that for the Doctor’s first freedom run into time and space that Barry Letts and Terrance Dicks didn’t choose to do a returning monster, or play it safe with a trip to a base under siege – both of which would have been entirely understandable especially in the anniversary series. Instead, we get the oddest first episode since Terror of the Autons, with two plots that seem entirely separate: the Doctor and Jo battle a plesiosaurus and an apparent time anomaly in 1926 while two carnival show people arrive on a planet of grey-faced bureaucrats.

The script isn’t Douglas Adams hilarious, but it’s a lot wittier than anything we’ve had since Robert Holmes last wrote for the show. Holmes’ natural tendency to write double acts shows in the Doctor and Jo’s easy banter: he’s keen to impress her with a trip to Metebelis 3, she can’t resist puncturing his pomposity, mocking his attempt to chat to some hens, then risking everything just to prove him wrong about his gut feel that they haven’t actually travelled back in time (it’s a smart move not to have restored absolute control of the TARDIS when the Time Lords handed it back to the Doctor), and wonderfully putting her ‘uncle’ on the spot when they are caught. A lot of people have called out the parallel relationship between Vorg and Shirna, another travelling showman with an assistant who’s both exasperated and adoring: Holmes makes the parallel obvious, probably to help reinforce the connections between what could otherwise seem rather disjointed and perplexing.

It’s also fascinating to see the third story in a row to focus on time anomalies (and the fifth in the last three years). With The Time Warrior and Invasion of the Dinosaurs coming up, there isn’t quite as much sustained focus on the plot possibilities of time travel until Moffat takes over. This is a really beautifully put together start to the serial with an energy and freshness that belies the fact it was made at the fag-end of the previous run and held over.

Next episode: Carnival of Monsters – Episode Two