Who is Doctor Who?

1. William Hartnell (1963 - 1966)

Forget Josef Fritzl, meet The Doctor. He first enters as a shady figure keeping a schoolgirl locked in a box in a junkyard. When two of her teachers try to rescue her from her "grandfather's" secret chamber, the nasty old man presses a button and his lair vanishes.

In a move that had 60s children's jaws dropping, the dodgy old man's police box is actually a time machine, taking its inhabitants from prehistoric Earth to the home of the Daleks, from the acid seas of Marinus to a planet of giant ants.

The first Doctor is a reluctant hero in the same way that Indiana Jones isn't that fond of snakes - he regularly tries to kill his companions, shouts and bullies alien menaces, and longs for a quiet sit down and a chance to smoke his pipe.

Early Doctor who was very different from David Tennant's era - sickeningly ambitious, recorded as live in a tiny studio 40 weeks a year - there were very few special effects, and William Hartnell frequently forgot his lines, leaving his companions to make the most out of his improvised word salad, defeating the Daleks with "radiation gloves" and "flosflosflosphorescent light" or they'd end up as "ciders hanging around in Spain".

Alamy

Best Bits:

The First Episode - Police Boxes were a common sight on the streets of 1960s London, and Doctor Who suddenly made each and every one magical.

The First Appearance of the Daleks - Originally the miserably mutated survivors of a nuclear war, the Daleks were killed off at the end of their first adventure, but brought back by popular demand. An insanely popular range of toys and films followed. The Dalek's designer was memorably paid £100 as a thank you.

The First Christmas Special - Nowadays it's not Christmas without the Doctor fighting Santa in the snow, but in December 1965 William Hartnell picked up a mince pie and a glass of sherry and wished "A merry Christmas to you all at home."

The First Regeneration - with no warning an exhausted William Hartnell fell to the floor and changed into someone else. "Coo!" gasped the audience.

Everett Collection

2. Patrick Troughton (1966 - 1969)

If the first Doctor had been a grumpy grandfather, the second Doctor was a funny uncle, and not in a gay way. Badly-dressed, shambolic and playful, Patrick Troughton defeated monsters with inventive fun - such as when he gave the Daleks a sense of humour, or killed a seaweed monster with amplified screams.

If the Doctor was more light-hearted, the aliens were more deadly, with serious complaints that the show was no longer suitable for children. Every story brought an even more outlandishly horrible threat - from the killer Octopus of Atlantis to Robot Yeti on the Underground.

Everett Collection

Best Bits:

The Early Cybermen - first showing up in William Hartnell's last story, the Cybermen really took off with the Second Doctor. They captured the moon, and invaded St Paul's Cathedral.

Patrick Troughton - the best thing about black and white Doctor Who apart from the Daleks, Troughton lights up any scene he's in, both deadly funny and childishly serious, whether he's being terrorised by Daleks with a drinks trolley, or menaced by Clockwork Soldiers.

Smoke and Foam - strapped for cash, the producers took advantage of a discount if they used the BBC's new foam machine. Shaving cream has never been more frightening - invading the Earth several times.

The Time Lords - in Patrick Troughton's last story we suddenly learn who the Doctor is - a Time Lord on the run from his own people. They catch up with him, put him on trial, and sentence him to live on Earth with a new face.

Rex Features

3. Jon Pertwee (1970 - 1974)

Doctor Who was now in colour - the HD of its day. With no real increase in budget, the producers saved money by stranding the Doctor on Earth, working with UNIT - a secret military organisation devoted to fighting off alien menaces (usually three men in monster suits in a field).

The programme became more grown-up, tackling radical threats such as global warming, alternative energy and chemical pollution, while also using A LOT of colour.

Jon Pertwee was a very different Doctor - a dashing action hero, proficient in Venusian Karate, driving a nippy sportscar, and addicted to his sonic screwdriver. An established comedian, Pertwee played it brilliantly straight, did his own stunts, and hid his lines on bits of the set to save learning them.

Everett Collection

Best Bits:

The Master: With the Doctor unable to leave Earth, his enemies had to drop by. The Master was introduced as a returning nemesis, and spent 1971 turning up as the surprise villain... in every story. Charmingly played by Roger Delgado, the character gained Jon Pertwee's fury by getting almost as much fan mail as the show's star.

UNIT: The Doctor suddenly had a family - the cuddly Bridgadier, scatty Jo Grant and some rugged soldiers who got zapped regularly.

The Autons: Killer shop dummies, the Autons were lethal plastic, and in the 1970s there was A LOT of plastic - we saw them dispatching their victims with artificial flowers, inflatable chairs and a range of lethal toys that were definitely a choking hazard. It's hardly surprising that they showed up again in the new series.

Sarah Jane Smith: As a reaction to the perception that all the Doctor's companions were scatty girls who screamed a lot in came feminist journalist Sarah Jane Smith. Who screamed a lot. She now has her own series.

The Reunion show: For Doctor Who's 10th Anniversary the three Doctors were reunited in an epic adventure that was officially the most exciting thing ever. Patrick Troughton took great delight in ad-libbing his lines and hiding Jon Pertwee's cue cards.

Rex Features

4. Tom Baker (1974 - 1981)

The first three Doctors had been established actors with great careers. When Tom Baker was cast he was working on a building site, but quickly made the part his own, insisting on a long scarf and companions who answered back.

Across eight wonderful years Tom Baker overcame the Loch Ness Monster, Egyptian Gods and budget cuts. After an increase in violence, the show became more comic, even employing Douglas Adams as a writer and script editor. Baker adapted to every change, making the part his own. When he finally left, a lot of children had no idea that the character could change his face.

Alamy

Best Bits:

Davros: The Time Lords send the Doctor back to meet the creator of the Daleks in a story that Russell T Davies claimed kicked off the Time War.

K-9: The Doctor got a funny robot dog as a companion. Serious science-fiction fans made loud tutting noises. Everyone else said "awwwww!"

Gallifrey: For the first time, the Doctor went back to his home planet and we got to see what the Time Lords were really like.

Romana: The Doctor got a Time Lady companion every bit as smart as him. Tom Baker got on so well with actress Lalla Ward that he married her briefly. She's now Mrs Richard Dawkins who has been in the new series playing himself which means... oh, that's complicated.

Alamy

5. Peter Davison (1981 - 1984)

Dashing Peter Davison wasn't even 30 when he was cast. Suddenly the Doctor was almost a romantic lead with a bevy of young companions. More vulnerable and less flamboyant, Davison spent three years dressed curiously as a cricketer, wearing a stick of celery in his lapel.

In a slight change of format, the BBC moved the series from Saturdays to twice-a-week. It was all a cunning plot to see if a midweek soap opera the BBC was developing would be a hit. The show was to be called EastEnders...

Loud and proud, 1980s Doctor Who wasn't afraid of big hair, thumping music and bright lights. Occasional use was made of the Top of the Pops set.

Rex Features

Best Bits:

Peter Davison's Last Story: Real Doctor Who fans gets all misty-eyed over The Caves Of Androzani. It had a great script, and a director who finally turned the lights down a bit. As funny as a visit to the dentist, it's the classic Doctor Who story you can watch without shame. Apart from the dragon.

The 20th Anniversary: All five Doctors running around a quarry in Wales. Well, three of them, a bloke who looked a bit like William Hartnell and a waxwork of Tom Baker.

Adric Dies: In a ratings-grabbing move, the Doctor's young companion got blown up. It was the first time a long-running assistant had got the chop and a nation's children went into mourning - although you can see the cast fighting to hold back the giggles on the DVD.

Nicola Bryant: The Doctor's sexiest-ever companion was introduced in a bikini. David Tennant says this was a very important moment in his adolescence.

Rex Features