Frankly, anyone can create an all-powerful monster or villain, one who can’t be killed but kills indiscriminately, one who is big enough and bad enough to be Big Bad enough to be a threat to the entire universe. It’s the smaller, damaged monsters of the week that are more difficult and therefore, ultimately, more rewarding.

This is the inevitable challenge behind ‘Flesh And Stone’: not only is it Part 2 of a continuing adventure after last week’s ‘The Time Of Angels’ (always going to have a slight dip in the tension), but also we’re required to learn more and be more scared by The Weeping Angels, the most disturbingly beautiful monsters since Pertwee faced off against the visitors from Axos. And so they have to have a Plan, with an Agenda. So, it’s smart that although the Angels are more brutal, vicious and terrifyingly powerful than before, they’re not The Doctor’s major concern. Frankly, he hasn’t got the time.

The job of any self-respecting Doctor Who writer is to not give a darn about the show’s continuity, but create a memorable and thrilling story. As long as any major plot points relating to the show’s history (or future) are kept helpfully ambiguous, the job of any fan boy is to whine about it a bit, then write up their own story that explains all the ‘mistakes’, ret-cons them into the existing history, or simply tells us why what went before was a absolute lie. The last time The Doctor found himself with a River, but without a paddle, we were warned about spoilers. This time, it’s all about continuity errors. Any questions you’ve had in the past five weeks will start to be answered with this episode. Although you might have to wait for a certain date in June for everything to fall into place. And if that’s not vague enough, we feel duty-bound to try and get through this review with little or no spoilers. Which is about as easy as finding someone who says they prefer the new day-glo Daleks.

‘Have I impressed you yet, Amy Pond?’, asks The Doctor at one point. Well, despite Matt Smith’s best efforts, that’s been a bit of a challenge thus far: he’s been rather shoved to the back of his own stories. That gets redressed in spectacular style this week, as finally, we’re reminded Who really is in charge around here. If you’ve not joined us yet because you’ve been delayed by time, tide or volcanic ash cloud, it doesn’t matter: the time is now. The Eleventh Doctor’s journey begins here.

There’s a fair bit of shouting and slamming fists on tables from young Master Smith, but there’s nothing to suggest that he’ll be known as ‘the shouty Doctor’ – this is simply the episode where Matt Smith’s Doctor takes centre stage and finds that time is running out. That’s not just a colourful, overused phrase. There’s so little time, in fact, that a Big Bad reveals itself mid-way through the episode, causing The Doctor to lose his nerve and show some moments of helpless frustration, particularly when things become so chaotic that one of the Cardinal Rules of a Steven Moffat episode is broken.

This is Doctor Who going up a gear and no longer leaving the brakes on: everything else in Series 5 has just been prologue. Add a line of dialogue that goes someway to explaining a throwaway gag in ‘The Next Doctor’, to a concept that could even justify some of the more controversial lines in Doctor Who: The Movie, and this episode really underlines the fact that nobody’s future – least of all The Doctor’s – is, well, set in stone.

There’s a moment (set aside a beautiful image of the TARDIS on the horizon that’s likely to be your new screensaver) where The Doctor finally realises that history can be re-written. This may not seem like such a big deal for your average Time Lord, but we’re not talking simply erasing memories of, say, a sudden appearance by Graham Norton, but something a lot more significant, and in The Doctor’s personal history.

And what are we talking about? Well. That would be a spoiler.

Airs at 6.25pm on Saturday 1st May 2010 on BBC One.