Crisis is an apt name for this episode – everyone knows it was a last-minute lash-up job from the original third and fourth episodes of the serial, which were apparently so tedious they had to be merged. It’s not noticeable – despite the change of director (Pinfield directed episode 3, Douglas Camfield episode 4).

What is noticeable is how much better this is than Dangerous Journey. It helps that this actually has a plot: discovering the ‘everlasting’ and thoroughly lethal properties of DN6, Ian and the Doctor resolve to stop it. The brazenness of this – reduced to the size of an inch, the time travellers are still determined to save the world – is excellent. It’s almost a metaphor for the series: the little people pitting their brains and bravery against the corruption and wickedness of giants, and defeating them. Forrester, who could crush the Doctor under his thumb, is destroyed by the ingenious use of a couple of corks, a Bunsen burner and (with exquisite irony) a spray can of insecticide. And given a petard is a small explosive, it’s difficult to see this as anything other than Forrester literally being hoist by his own petard.

Introduced in this episode is the Doctor’s pyromania. ‘There’s nothing like a good fire, is there?’ he asks, gleefully. Given his forthcoming responsibility for the arson of Rome, this all seems part of an attempt to make him seem even more like an anti-establishment figure – as if his adoption of the French Revolutionary Regional Officer’s cloak wasn’t indication enough. There’s then a hilarious exchange with Barbara when he casually mentions there’s going to be a huge explosion: this gleeful destructive streak is quite edgy, and very endearing, and it’s something we’re going to see crop up a few times (for example, the end of The Savages). It’s the kind of slightly unnerving oddness that both Cushing and Troughon pick up on (and even Hurndall has a hint of).

The decision to merge Crisis and The Urge to Live seems evidently the correct one. As a whole, Planet of Giants sags badly in the middle episode, but it’s bookended with two of the paciest episodes so far, both of which give the regulars a chance to work together with outsize props, which must have been fun. Certainly, they all look like they’re enjoying this one.

Other things I noticed:

• Another reference to a missing adventure – the Doctor and Susan were present during a (presumably) First World War Zeppelin air raid
• Hartnell looks great in waistcoat and shirt sleeves. It’s almost a pity he gets the coat back in the next story
• Contemporary Earth stories are never the same without comedy yokels – Hilda and Bert are the first of many squabbling couples to come
• No-one mentions that the TARDIS has finally landed in 1960s England despite this being the subject of lengthy discussions in both The Reign of Terror and World’s End

Next episode: World’s End