There’s a brief moment in tonight’s episode of The Hour when Marnie, hosting the renamed Name That Dinner Guest – formerly, in an earlier episode, simply Dinner Guest – eyeballs the camera and observes, ‘You need a sharp knife and a lot of pluck to bone the haunch’. It’s a moment of Nigella Lawson-style innuendo in an episode that loves the sound of its own dialogue rather too much.

This is the trouble with so stylised a drama as The Hour. Sooner or later, the style takes over and everything falls into the territory of pastiche. We’ve been concerned, for a while now, that this would be the trajectory of this series: that the clipped aphoristic voice of the period intellectual would so dominate proceedings that, somewhere between its starting point of newsroom thriller and its destination – essentially Brief Encounter with added typewriters – the plot would be lost.

And we’re afraid that it has come to pass. Not, it has to be said, in the excellent final ten minutes – of which more anon – but in the proceeding fifty. After a previous four episodes in which it looked like the plot was revolving around Soho vice, now it looks like the dominant story is of the government profiteering from its nuclear policy. At the heart of this is a shady organisation, Castle Corps, and the king of the castle, Defence Minister, Mr Satchell – a man about whom the plot obliges us to know very little, but who wanders into shot for subtext-laden conversations in which everyone pointedly says nothing, in bold type for emphasis.

It’s the kind of drama that demands expositional dialogue, of which there is no shortage. ‘Every office,’ we are told, ‘needs to find a safe place in the event of an [nuclear] attack.’ But it’s the knowing Fifties-speak that grates the most, when very good actors are obliged to deliver solipsistic philosophy that is less like journo-speak and more like something from the green eye of the little yellow god.

The greatest culprit by far is Randall Brown (Peter Capaldi), who is giving to telling stories about a man who cuts the legs off his bed in order to escape the monster beneath. ‘No man is sane,’ he observes, ‘who doesn’t know how to be insane on the proper occasions’, and for a brief moment, the action grinds to a halt as you speculate whether this is genuinely as clunky as its sounds, or whether one is, in fact, hearing a highly subtle portrait of a man who is given to hiding cliché behind the assumed disguise of a philosopher. The possibility is there.

But then one realises that everyone in The Hour – Sissy and Isaac excepted – has caught this disease, and is talking in this self-regarding sardonic manner. Take Freddie Lyon, whose inability to do anything with Bel seems less about his guilt at the departure of French wife, Camille – suddenly dematerialised from the narrative – and more about the inevitable romantic complications that ensue in a world where everyone is a narcissist: where the person who loves the hero most of all, we are told, ‘is the hero himself’.

There is human drama in the middle of all this, and it’s probably the awkward interplay between Isaac and Sissy, after the former learns of the latter’s engagement, that is the most affecting. It’s good to know that The Hour can attribute honourable intentions and behaviour to the non-firebrands too.

But it’s only in the last ten minutes that things really kick into gear, and The Hour finally delivers on the heart-pumping tension that was a characteristic feature of the first series. At last, everyone has a role: girl beater Laurie Stern, suddenly heroic but a dead man walking, too; dead-eyed Kiki out-manoeuvring him at the last, contemptuously teetering back into the gutter; McCain cornered and haunted – suddenly too tired to scheme; Marnie thrilling to the testosterone of it all and willing to welcome Hector back into her bed – all played to an insistent jazz soundtrack. It’s so electric it makes you wish the whole episode had been like that.

When Kiki whispers to Freddie, ‘They will kill you’, for a moment, you believe it. But will things escalate tomorrow night or has The Hour played its final ace? With so thrilling but so frustrating a drama, it’s very hard to tell.

Aired at 9pm on Wednesday 12 December 2012 on BBC Two.

> Buy Series 1 on DVD on Amazon.

> Order Series 2 on DVD on Amazon.

What did you think of the episode? Let us know below…