The Firemaker (100,000 BC Episode 4)

The one where Susan actually has a good idea for an escape...

The Firemaker is probably the least of the three prehistoric episodes of this serial, with Waris Hussein's so far wonderful, imaginative direction faltering somewhat at the final hurdle. But we still have the ingenious characterisation of Anthony Coburn's script, and here we see the Doctor using his cunning to turn the tables on their captor Kal.

The Doctor tricks Kal into showing the tribe his knife, with Old Mother's blood on it ("This knife shows what it has done", he asserts), and the tribespeople realise their new leader killed an elder to steal his power. This is the first time we see the Doctor topple somebody from their lofty tower, the first in a very long line of overthrown governments and fascist leaders.

The Forest of Fear (100,000 BC Episode 3)

The one where the Doctor is caught planning to murder an injured man...

At the top of this episode the Doctor apologises for getting them all into this mess, claiming it's all his fault. But when you think about it, it's not his fault at all. All he did was go exploring and he was violently abducted and imprisoned. This isn't like his recklessness in the next serial, when they visit Skaro and he purposefully sabotages the TARDIS so that they're forced to explore the alien city. This time he is purely a victim of circumstance and has had little active part to play in getting them into trouble.

Eileen Way, who plays Old Mother, was only 52 when she recorded this serial, but make-up supervisor Elizabeth Blattner does a great job of ageing her up and making her look much older than she is. As she grabs Za's stone and stares impassively into camera we're treated to another example of how director Waris Hussein likes to focus closely on faces to sell the story and dialogue.

The Cave of Skulls (100,000 BC Episode 2)

The one where the Doctor lights a pipe and gets abducted by cavemen...

After waiting an entire week (or in the case of those watching back in 1963, just a few moments since the repeat of episode 1), the story resumes by reminding us where the police box has landed, and that a hirsute stranger is watching. But then our curiosity is deprived of more as we cut to a bunch of well-spoken cave dwellers trying to light a fire.

Director Waris Hussein populates the cave set with an awful lot of extras (18 uncredited supporting artistes, in fact) to create the idea that this is quite a large tribe of pretty desperate people (ten men, nine women and four children). Za is trying to conjure fire, as his late father did before him, but when the tribe turned against his father and killed him, the secret of firemaking was lost. Za is hoping to become undisputed leader of the tribe by sparking up again, but his methods range from the amusing (shouting at a stack of twigs) to the desperate (rolling a bone between his palms and sprinkling dust over it).

An Unearthly Child (100,000 BC Episode 1)

The one where two curious school teachers interfere in something best left alone...

It's been said before, and it'll be said every time somebody new sees An Unearthly Child for the first time - this has to be one of the finest first episodes of any television programme, ever. We all know that the first attempt at filming it wasn't up to scratch (but isn't it lovely we can see that too?), but for saying it was produced by an inexperienced 27-year-old and directed by a 24-year-old, the achievement stands the test of time considerably. A lot of the success has to go to writer Anthony Coburn too. He was 35, but not exactly an old hand either.

Right from the very first second, An Unearthly Child is astonishing. Those opening visuals and that theme music would have knocked the socks off the audience back in 1963 - the looping, undulating, ever-so-slightly-threatening score by Delia Derbyshire and Ron Grainer perfectly matches Bernard Lodge's ethereal, mesmeric, hypnotic "howlaround" graphics. In 1963, it was like nothing ever seen before, and even today, it remains almost unique, its bewitching power undiminished.