Do you remember what The Doctor told Amy when she was seven years old? And, more to the point, do you remember what we told you in our review for ‘Flesh And Stone’? Just two little words: continuity errors. Two words that become ever more important now, because, let’s face it, we’re on the final stretch now. Once this episode has aired, we have just two stand-alone episodes, and then the final, two-part finale (some details of which are seeded in this episode).

Elsewhere, anyone expecting things to pick up pace after the slow drip-feed of last week’s opener ‘The Hungry Earth’ are going to be seriously frustrated: ‘Cold Blood’ is a somewhat uneven, almost anti-climatic episode. What’s intriguing is that you suspect that’s rather the intention, in that it feels very much like a pre-1970’s episode, with a good deal of dialogue replacing action. This means that the very youngest fan in your household might get bored occasionally, whereas the very oldest fan could even hanker for more episodes of the same, with equal pace and plotting.

In that respect, there’s lots of pleasing Pertwee-style shenanigans: a little of ‘Frontier In Space’ as The Doctor attempts to broker a peace between two species. While it’s during this section that the kids might get fidgety, and you’re aware that Who can’t afford to have these kind of scenes too often, it is nice to actually see The Doctor doing what we know he must spend a good deal of his time doing – acting as an ally between two potentially warring races.

The Silurians (as they’re not called here) have always been one of the series’ most complicated villains in that they’re not actually villains, and this episode’s main stumbling block is that essentially only one voice is given to the sympathetic and liberal quotient of the slumbering beasts, allowing the more militant might to take over, running the risk of reducing this week’s monsters to just that: monsters.

However… we’ll avoid spoilers (we’re nice like that), but if you’re good at reading between the lines and picking up clues, we suggest strongly that you skip the next paragraph.

For most of this episode, we were considering three stars. Now, three stars isn’t bad, but for most of the episode, we couldn’t deliver that fourth star. If you want to remain confused, look away now. Something happens, something pretty important, and it leads to a fierce – but inevitably brief – argument aboard the TARDIS. It follows the theme of Silurian stories not going the way The Doctor would hope. While The Doctor doesn’t join in with the waving goodbye in the churchyard – he’s still more interested in what Amy can remember – we’re allowed, once again, to see what beautiful little nuances Matt Smith brings to his Doctor, particularly when, as happens this episode, he’s simply not in control. The image of his face as the episode closes on The Doctor holding A Very Important Thing is of a confused, lost and genuinely terrified Time Lord.

But before all that, we get to see The Doctor railing at the humans, in a way he hasn’t since the Colin Baker era. Sure, there was Eccleston’s teasing and irritated air, but in this episode – since some bad decisions are made by some good people – we realise that, although this man has all the time in the world, he can’t always afford to have that much patience. There are bigger things out there, more important things. And, as he tells us, not everything is fixed. Some things can be changed.

Airs at 7pm on Saturday 29th May 2010 on BBC One.