Dalek

No-one could accuse Russell T Davies of lacking commercial sense. An old monster in Episode One to reassure the fans. Half the budget thrown at Episode Two to convince the CGI generation this stuff is worth watching. A gloriously historical Episode Three to flex the BBC's period drama muscles. Then relax with a money-saving two parter, coasting on the show's newly established success... And then, just as the rating starts to sag with the traditional mid-season slump - WHAM! Hit 'em with a Dalek.

Now THAT'S Doctor Who.

Previews suggested Dalek would be the pick of the season, and expectations were consequently enormously high for this episode - although perhaps not much higher than they would have been anyway, with the iconic nature of this, the Doctor's oldest foe. The BBC's pan-media publicity outlet ground into action once more after a lull for Aliens of London / World War III: a new-look Dalek graced the cover of the Radio Times; trailers popped up at all hours of the day; Blue Peter worked its usual behind-the-scenes-feature magic; Newsround Showbiz carried a feature on the story, although not until after the show aired... Even BBCi managed to make a story out of it, focusing on the monster's new abilities.

Ultimately, the episode probably ended up commanding almost the same level of public attention as Rose, the new season's opener - and much like that story, it succeeds absolutely in recreating an icon for a new generation, mixing the traditional with the innovative to invent a whole new, even more satisfying creation. The tight cast, high production values, impressive direction and top-notch visual effects are everything people had been demanded of the new Dalek, and indeed everything they should now be coming to expect from the series, but it's the writing that's the real start of this episode. It was always going to take more than a bigger laser to evolve the Dalek from a prop that crops up in Kit-Kat adverts into a really scary alien, and Rob Shearman absolutely cracks it, creating instead something that goes beyond all that and becomes, at times, genuinely moving.

The self-consciously traditional prop/costume design belies a new direction for what is a supposedly a 'monster' story, with a tense, claustrophobic storyline that makes the most of its 45 minutes by filling it with moral greys and difficult decisions rather than great big explosions. Gone are the massed armies of yester-who, the 10,000 Daleks waiting just off camera to annihiliate the universe - here we have a single lone Dalek, against a single, lone Doctor; both of them intelligent, and both of them dangerous. The result is an exquisite pair of performances, each one bouncing off the continuing wonder that is Billie Piper, and each character (and yes, it is a character) bringing out the best and the worst in the other. Between the three of them - amongst all the mayhem, and despite the occasionally overbearing incidental music and now-traditional wobbly editing - they create what are undoubtedly some of the strongest moments ever seen in the series.

Genuinely, it's hard to say much about this episode other than how good it is. It's scary, it's funny, it's tense, it's almost impossibly involving, and it's got lines that will send a thump of energy right through your tragic geeky heart. And it's got the best cliffhanger ever written, right there in the middle of the episode. And not only has it got all this, and profound emotional arcs, and powerful, moving moments of drama, AND great big explosions, it's also got the cute gay bloke off of Corrie.

Never mind aiming at the eyepiece, this one hits you right between the eyes - and stays there.