William Hartnell's Doctor - Professorial and cantankerous

The first series was born out of the space soap operas of the 1950s and the need for a new Saturday teatime drama to sit between Grandstand and JukeBox Jury.

1960s

William Hartnell's professorial, cantankerous Doctor first appeared on our screens on 23 November, 1963 and six more actors have played the Time Lord on TV since.

When ill-health influenced Hartnell's decision to retire the producers hit upon the idea of continually re-casting the lead role, and the famous regeneration powers of the Doctor emerged.

Patrick Troughton brought new lightness

Patrick Troughton took possession of the Tardis in 1966 and brought a new lightness to the role.

He also helped establish the idiosyncrasies of the Doctor - which each new lead actor would create, adapt and add to over the years - and many of the themes of the character were introduced.

The concept of the time lord and of his ancestry were introduced in plot lines during Troughton's era.

1970s

But after three years in the role he stepped aside and made way for Jon Pertwee who brought a more dynamic and colourful edge to the series.

Jon Pertwee's Doctor was exiled to Earth

After years of travelling through space and time Pertwee's doctor found himself exiled to earth and many of the episodes had a distinct James Bond feel.

Ten years after the screen debut of Doctor Who, the three Doctors met up in an anniversary special but Pertwee bowed out in a story line which saw him bitten by a radioactive giant spider.

Tom Baker took over in late 1974 and spent seven years as the time-traveller, bringing a lighter and wittier touch to proceedings, helped in part by the writing of Douglas Adams, the author of Hitchhiker's Guide to the Galaxy.

Part of the charm and attraction of Doctor Who was the inventive use of monsters and villains and the Time Lord's companions in the series.

Tom Baker spent seven years in the role

The Daleks, Cybermen, Davros, and the Master are among the most villainous of the Doctor's adversaries while along the way he has been aided by assistants such as Susan, Zoe, Brigadier, Adric, Tegan, Peri, Mel and Ace.

A highlight of Tom Baker's tenure was the introduction of K-9, his robot dog assistant with a killer laser in his snout.

1980s

Tom Baker brought a more authoritative edge to the Doctor and played him as a genius, often distracted or irritated by the failings of others.

Peter Davison was the youngest Doctor

In 1982 Peter Davison, known to millions as a vet from All Creatures Great and Small, became the fifth doctor and spent three years in the role.

For the 20th anniversary the five doctors were reunited in a one-off BBC special and the BBC held a massive convention in Longleat House, Wiltshire.

Colin Baker took over in 1984 and is described by the BBC Doctor Who website as the "most eloquent and poetic" of all the Doctors.

But ratings for the show began to drop and after a hiatus in 1986 the programme was reduced to 14 episodes a year and a new Doctor was sought.

Scottish actor Sylvester McCoy took over in 1987 but his reign was just two years.

Colin Baker has been called the most eloquent Doctor

In 1989 Doctor Who was cancelled to the disappointment of fans around the world.

1990s

Many attempts to revive the series failed but hopes were raised in 1996 when Paul McGann took over the role for an Anglo-American TV movie.

Despite criticisms that the Time Lord had been Americanised it was received well in the UK with more than nine million viewers but it went down poorly in the US and plans for a spin off series were shelved.

Sylvester McCoy returns as the Doctor in an online special

Since then fans have had to rely on videos of past episodes, audio cassettes and new adventures in print - until now.

Death Comes to Time is the first original and authentic Doctor Who story for five years with Sylvester McCoy back at the helm of the Tardis.

Time, it would seem, never stands still for Doctor Who.