BBC1 - 12th April 2008 - 6.45pm

“You held her off with a waterpistol? I bloody love you!”

Ladies and gentlemen…the prologue. And it came to pass that yet another fine episode appeared before the assembled masses.

The series turns on a sixpence yet again and, after last week’s light hearted romantic comedy, writer James Moran explores the Doctor’s moral choices whilst framing his dilemma in the tragic events at Pompeii. No other television programme really has the ability to do that.

Certainly for the first 15 minutes it is a bit of a slow burn and the introduction of Caecillus (Peter Capaldi on fine form) and his family (Tracey Childs as Metella, Francesca Farmer as Evelina and the rather lovely Francois Pandolfo as Quintus) seems disjointed and slightly out of place because modern speech patterns are being used. It’s almost as if ‘My Family’ has been transposed to AD79 and it took me a bit of perseverance to accept it. When you’re used to watching a series like ‘Rome’, for example, this feels very different and I’m not sure it entirely succeeds especially when it extends to Phil Cornwell’s tradesman channeling Del Boy. But we do get exceptional production values and location shooting to make the episode look ravishing and sumptuous. And it’s lovely to have the Doctor referencing ‘The Romans’ with his comment: "But that fire, nothing to do with me! Well, maybe a little bit..." as he discusses what he assumes is Rome on arrival with Donna.

Going back to the modern speech patterns you could argue that this is also a reminder of the theme established in ‘The Shakespeare Code’ about the power of words and language. Hence, we get the pure visual communication of the Sybeline prophecies, the running gag about Latin/Celtic translations and the very accurate point about how the events in Pompeii create new words like ‘volcano’ that are part of the very language we use now. This is as much about ‘what did the Romans ever do for us’ and their cultural impact as it is about rock monsters and the Doctor’s humanism. Even then the notion of the ancient and modern roots of language echoes the fixed and in flux nature of history as observed by the Doctor.

However, minor problems aside, the story moves up a gear when the Doctor and Donna are identified by Lucius (Phil Davis, still channeling Albert Steptoe perhaps) and we get some further foreshadowing from his prophecies. What is on Donna’s back? What is the Medusa Casade? All very intriguing and a good hook to keep the observant viewer happy. What’s interesting in this episode is that the plot almost mirrors that of ‘Partners In Crime’ where again we have aliens attempting to reproduce themselves by exploiting the human body because, mysteriously, their planet of origin has been ‘lost’. Is this theme of 'reproduction by any means necessary' a recurring one, I wonder?

Then after the slow start it all moves into high gear with the Doctor’s confrontation of the Sybeline Sisterhood (a neat bit of male reason versus feminine intuition), the attack by the adult Pyrovile and Donna and the Doctor’s escape into the heart of Vesuvius. The effects, both CG and prosthetic, are excellent and the epic scale is maintained by director Colin Teague. Once inside the Pyrovile pod, the moral choices and high stakes of the story are finally revealed. When the Doctor realises that his choice must be to cause the eruption of the volcano to save the world there is a sense of inevitability that he and Donna share as they both, in a highly charged scene, press the destruct button and seal the fate of Pompeii.

The central argument of why and when the Doctor is not allowed to interfere with history is emotively made and takes us back to similar discussions in such early stories as ‘The Aztecs’. The Doctor’s anguish is clear but he has to contend with Donna, who like Barbara, refuses to acknowledge the brutality of the Time Lord’s responsibilities. This moves beyond the original notion of ‘The Aztecs’ as it shows a passive Time Lord simply cannot abandon 20,000 people and a determined companion arguing that he must do something ‘human’. The cold shoulder that the Doctor gives to Caecillus and his family as they huddle in the fall-out and he rushes into the TARDIS is an incredible moment and it takes Donna to force him to go back and help them and for him to recognise that she was right in ‘The Runaway Bride’ – he needs someone to stop him. That final, tearful plea from Donna is a truly moving scene and in it Catherine Tate firmly enshrines Donna into the roll call of the series best companions.

The coda with Caecillus and his family standing on the hillside overlooking the devastation of Pompeii is brimming with sad reflection and shock for the victims they've left behind and symbolises our own ongoing fascination with this moment of history. And as the TARDIS departs that is where the story should end but unfortunately there is a trite epilogue that depicts the surviving family worshipping the Doctor and Donna as their household gods that, for me, takes the edge of the very powerful drama we have just witnessed. But again a minor problem for a stunning episode that demonstrates a production team working at full tilt, a script asking some searching moral questions and an ensemble of actors, and especially Tate, delivering great performances. Marvellous.