When Doctor Who began on BBC television in November 1963, its premise offered almost unlimited room for change. A mysterious traveller, a police box that is larger inside than outside and companions willing to step into the unknown could carry a story to ancient history, a distant planet or an ordinary British street made suddenly strange. The original run, from 1963 to 1989, kept testing what that premise could do. Its effects and fashions changed, but its curiosity remained the constant.

Where the journey began

The first story, An Unearthly Child, begins with two teachers investigating their unusual pupil Susan Foreman. They follow her to a junkyard and discover the TARDIS and her grandfather, the Doctor, played by William Hartnell. The early Doctor is not yet the reassuring hero later viewers may expect. He can be guarded and difficult, which gives Susan and teachers Ian Chesterton and Barbara Wright important work to do as the audience’s guides.

The TARDIS makes the series flexible, but the companions make it human. They ask the questions viewers would ask, challenge the Doctor and react to worlds that he may treat as familiar. That relationship becomes a defining pattern even as the travellers and the shape of the adventures change.

Why the Doctor could change

In the 1966 story The Tenth Planet, Hartnell’s Doctor transforms into a new incarnation played by Patrick Troughton. The idea was first presented as a kind of renewal; the name “regeneration” came later. It solved a practical production problem and gave the programme a lasting dramatic possibility: the central character could remain the Doctor while acquiring a different manner, energy and way of relating to others.

Troughton’s more playful Doctor did not erase Hartnell’s version. Instead, the change established that contrast could become part of the series. Each new performance asks the audience to recognise the same traveller in a different person. That is why a change of lead can feel like a new beginning without requiring a new programme.

From Earthbound adventures to a wider universe

The Third Doctor, Jon Pertwee, brought a brisker, more action-oriented style. His association with UNIT gave stories a recurring organisation and a recognisable Earth setting. Tom Baker’s Fourth Doctor then made eccentricity and unpredictable humour central to his performance, while stories ranged from gothic suspense to broader science fiction. Elisabeth Sladen’s Sarah Jane Smith, who travelled with both Doctors, shows how a companion can carry continuity across a major change.

The 1980s brought further reinvention through Peter Davison, Colin Baker and Sylvester McCoy. Their Doctors differed in temperament, and the programme continued to try new tones. The relationship between McCoy’s Doctor and Ace, played by Sophie Aldred, gave the final seasons a particularly strong focus on a companion’s history and choices. The 1989 story Survival closed the original regular run, though it did not close the possibilities of the character or the TARDIS.

Monsters, mysteries and ideas

The Daleks and Cybermen became recurring threats, but a classic Doctor Who story need not depend on a familiar enemy. Its best adventures make an unfamiliar place worth exploring and give the Doctor a problem that cannot be solved by force alone. The series can be eerie, funny, political or fantastical, sometimes within one serial. A limited studio setting may make the design conspicuous, yet that theatrical quality also asks viewers to meet the programme halfway with their imagination.

The show’s changing form is part of its history. Early stories could use long serials and historical settings; later production teams pushed towards different mixes of suspense, action and character. Rather than treating one era as the definitive version, it is more rewarding to notice how each makes use of the same basic invitation: step into the TARDIS and see what is around the next corner.

Where to start with classic Doctor Who

An Unearthly Child is the natural starting point for the original premise. The Tenth Planet matters for the first change of Doctor, although part of its original television recording is missing. For a different entry point, try a Pertwee or early Tom Baker story and watch the interplay between Doctor, companion and setting. Finally, sample a McCoy and Ace story to see how far the series had travelled by 1989. The pleasure is not in completing every episode first; it is in finding an era that makes you want another journey.

Featured image: existing site illustration of the Jon Pertwee and Tom Baker eras. This guide covers the full original run.

Sources: Doctor Who: An Unearthly Child; Doctor Who: the history of regeneration; Doctor Who: Tom Baker’s debut season; Doctor Who: Survival.