Chapter Five screams “penultimate”. It’s nowhere as exciting as Chapter Four but it does advance the Flux storyline and Chris Chibnall’s wider myth-making scheme, while showing Grandmaster Chibs placing characters in key positions on his multi-dimensional chessboard, poised to make his last moves.

Among several holding patterns, the most impressive is ‘Around the World with Professor Jericho’, who is in full Phileas Fogg mode with his companions Yaz and Dan. To be fair, it’s more sharp-as-a-tack Yaz (Mandip Gill) and her blundering associates Jericho (Kevin McNally) and Dan (John Bishop). Stranded in the early 1900s, the trio are doggedly pursuing a vague directive from the Doctor, which leads them from Mexico to Constantinople to Nepal to the Great Wall of China, and thence back to Liverpool (looking spectacularly un-sooty for 1904). The joke’s on them; they could have stayed in Blighty.

Lots of fun is had along the way, with counterweight-pulley pratfalls in an Aztec tomb (surely a little nod to the pulley system made by William Hartnell’s Doctor in The Aztecs, 1964); a mickey-taking hermit halfway up the Himalayas; the graffiti-message-across-time daubed at the Great Wall; and Dan getting ribbed for being repetitively Scouse. The time-hopping tunnel-builder Joseph Williamson falls into place, too. On an ocean liner, there’s also a tender moment when Yaz watches her Doctor-hologram for clearly the umpteenth time and we observe how much she adores and misses her friend.

The Time Lord, meanwhile, overcomes last week’s cliffhanger – petrification into Weeping Angel – with remarkable ease, while the Angels themselves are fast dispensed with like last week’s cat litter. Beyond our universe, the Doctor is in the company of an Ood and that mysterious taunting figure from Chapter Three. “I’m the one who found you,” she now chooses to reveal. “I brought you to Gallifrey and raised you. I am Tecteun. The woman you used to call ‘Mother’.” These exposition-laden moments, teasing about the Doctor’s origins, are altogether less tedious than equivalent scenes in The Timeless Children – and gain import and grandeur in the hands of Barbara Flynn and Jodie Whittaker (both magnificent). Flynn is so fabulous as Tecteun that I flinched when that camp swine Swarm swanned in and, with a stroke of his glove, made her “sashay away”.

Not content with expanding the Time Lord’s backstory, Chibnall wades into Unit’s already messy timeline… and muddies it further. In his new potted history, the United Nations Intelligence Taskforce (latterly Unified Intelligence Taskforce) has been malignly influenced by the Grand Serpent aka Prentis (Craig Parkinson). Far more menacing than in Chapter Three, he’s been bumping off big wigs for decades, although it isn’t clear how his sickening serpent gets inside his victims to begin with. Also, how did Jon Pertwee’s exiled Doctor never bump into Prentis during his many years at Unit or spot the fully functioning Tardis they’ve mothballed? In a sweet, fleeting aside, circa 1967, the man who would become the Brigadier is heard off-stage (a snippet of Nicholas Courtney from Terror of the Autons). But surely he could never have served as a corporal, as described; Lethbridge-Stewart was always officer material.

Prentis’s encounter with the Brig’s daughter, Kate Stewart, shows what a shrewd operator she is – and Jemma Redgrave is on redoubtable form, returning for the first time since The Zygon Invasion/Inversion six years ago. I was dismayed when Chibnall summarily terminated Unit in 2019’s Resolution. Especially because he had told me in 2012: “As a writer, you’re eternally grateful to everyone back in 1968 who came up with that idea because it’s a brilliant storytelling mechanism. Unit is embedded into the family history of the show.” Now the time is ripe for Kate and Unit to regain their former status – and save planet Earth.

In further Chibs chess moves, Vinder is paired up with Dan’s date Diane inside a Passenger, while Bel is “hyperjacked” by Dan’s dog-man Karvanista. Earth has become – as ever – the focus in the universe for ultimate destruction by the Flux, the Division and marauding Sontarans. And, of course, in another dimension the Ravagers are dangling the Doctor’s lost memories in a fob watch. Are we all keeping up…? Is everyone poised? Only one more Chapter to go…

• Catch up on all the Jodie Whittaker adventures in the Radio Times Doctor Who Story Guide

Read our previous reviews of Doctor Who – Flux:

• Doctor Who – The Halloween Apocalypse review
• Doctor Who – War of the Sontarans review
• Doctor Who – Once, Upon Time review
• Doctor Who – Village of the Angels review

Read more about Doctor Who:

• Doctor Who: Survivors of the Flux podcast review
• Doctor Who: Survivors of the Flux’s 9 biggest questions
• Doctor Who’s Survivors of the Flux poses more questions about the Doctor’s origins
• Doctor Who’s Brigadier cameo makes an even bigger mess of UNIT dating
• Can Doctor Who: Flux stick the landing?
• Doctor Who star teases “confrontation and destruction” in Flux finale

Doctor Who continues on BBC One on Sundays. For more, check out our dedicated Sci-Fi page or our full TV Guide.