In the 2005 series, the keys are also remotely linked to the TARDIS, capable of signalling its presence or impending arrival by heating up and glowing.

In " Utopia " ( 2007 ), and in " The Dalek Invasion of Earth " ( 1964 ), the TARDIS was shown to have an internal deadlock ; once thrown, it would prevent entry even for authorised users with authorised keys.

" Several people have managed to just wander into the TARDIS without any problem over the years, including some who became companions ; since the TARDIS uses keys, it could easily have been left unlocked.

The most famous of the Workshop's creations using ' radiophonic ' techniques include the Doctor Who theme music, which Delia Derbyshire created using a plucked string, 12 oscillators and a lot of tape manipulation ; and the sound of the TARDIS ( the Doctor's time machine ) materialising and dematerialising, which was created by Brian Hodgson running his keys along the rusty bass strings of a broken piano, with the recording slowed down to make an even lower sound.

By this time TARDISes have evolved to point where they appear human and reproduce sexually ( the Doctor's companion Compassion is the first such TARDIS ).

Like the TARDIS, it has become one of the icons of the programme ; spinoff media such as The Sarah Jane Adventures and Torchwood have replicated its functions in devices such as the sonic lipstick, sonic blaster, sonic pen and sonic modulator.

It is shown to have been created by the TARDIS as part of its automatic regeneration.

The Doctor's TARDIS was for most of the franchise's history said to have been stolen from the Time Lords ' home planet, Gallifrey, where it was old, decommissioned and derelict ( and, in fact, in a museum ).

The dimensions and colour of the TARDIS props used in the series have changed many times, as a result of damage and the needs of the show, and none of the BBC props has been a faithful replica of the original MacKenzie Trench model.

Susan Foreman, the Doctor's granddaughter, claimed to have coined the name TARDIS: " I made up from the initials.

In " The Curse of Peladon ," after the TARDIS falls down the side of a cliff, the Third Doctor remarks that it " may have its faults, but it is indestructible.

In " Frontios " ( 1984 ), the Fifth Doctor believes the TARDIS to have been destroyed in a meteorite bombardment, apparently contradicting the earlier claim of indestructibility.

In " The Eleventh Hour " the TARDIS completely changes after crashing, and the Doctor's comment " What have you got for me this time?

The spin-off media have, on a number of occasions, had the TARDIS wait around for the Doctor for decades and even centuries in relative time.

The TARDIS says that she deliberately allowed the Doctor to " steal " her, as she wanted to see the universe itself ; in a reversal of the traditional view, the TARDIS claims to have stolen the Doctor.

Cosmetically, the police box exterior of the TARDIS has remained virtually unchanged, although there have been slight modifications over the years.

As the TARDIS does not have a second set of inner doors in the revived series, the interior side of the police box doors – complete with the police telephone mounted on the inside of the cupboard door – are seen from the control room.

In " Boom Town ", the Doctor simply noted that humans do not notice odd things like the TARDIS, echoing a similar sentiment expressed by the Seventh Doctor in Remembrance of the Daleks ( 1988 ), that humans have an " amazing capacity for self-deception ".

Newer TARDIS models apparently have more advanced locking mechanisms that are touch-sensitive or may be operated by remote control.

" Utopia " presented, for the first time on-screen, a circumstance in which a character travels on the exterior of the TARDIS during a flight, when Jack Harkness was somehow able to grab hold of the TARDIS as it began to dematerialise and hold on to its destination ; the episode does establish, however, that a normal person would not have survived the trip, as Harkness is " killed " by the experience, but due to his immortality, soon revives.

The Time Lords are able to divert the TARDIS's flight path (" The Ribos Operation " ( 1978 )), or have the ability to totally override and recall any TARDIS by the order of the Council (" Arc of Infinity " ( 1983 )).

The TARDIS lock's security level has varied from story to story.

* Although the TARDIS interior changed several times throughout the original series, the movie's set was the most dramatic change yet, replacing the sterile white corridors and " roundel "- based design with a steampunk theme reminiscent of Jules Verne.

He was also hired by the BBC as the concept artist for the 2005 relaunch of the Doctor Who television series, having particular input into the design of the TARDIS interior set.

In September 2010, MIT students attempted to put a TARDIS, the time machine from the BBC's Doctor Who, onto a roof.

The Eye provides the power required for time travel ( The Three Doctors, 1973 ; The Deadly Assassin, 1976 ), and all Time Lord TARDIS time machines draw their power from it ( the 1996 television movie ).

" In " The Parting of the Ways ", the Doctor mentions that when Emergency Program One was activated, the sonic screwdriver would receive a signal from the TARDIS.

The Doctor later receives a new one, which emerges from the newly-regenerated TARDIS console.

The TARDIS used from 2005 to 2010 on display at BBC Television Centre

They are also said to draw power from the entire universe as revealed in the episode " Rise of the Cybermen " ( 2006 ), in which the TARDIS is brought to a parallel universe and cannot function without the use of a crystal power source from within the TARDIS, charged by the Doctor's life force.

Another form of energy, " huon energy ", is found in the heart of the TARDIS and ( apart from the activities of the Torchwood Institute ) nowhere else in the universe (" The Runaway Bride ").

However, the Doctor's TARDIS has been seen to be able to fly through physical space, first in " Fury from the Deep " ( 1968 ) and at repeated times throughout the revived series, most notably in " The Runaway Bride " ( 2006 ), in which the TARDIS is shown launching into space ( most previous incidents show the TARDIS flying only after it has dematerialised from a location ).

Apart from the ability to travel in space and time ( and, on occasion, to other dimensions ), the most remarkable characteristic of a TARDIS is that its interior is much larger than it appears from the outside.

As seen in " The Trial of a Time Lord " ( 1986 ), the experiences of the TARDIS and its crew can be recorded and played back from the Matrix, the Time Lord computer network that is the repository of all their knowledge, as well as the memories and experiences of deceased Time Lords.

The entrance to the TARDIS is capable of being locked and unlocked from the outside with a key, which the Doctor keeps on his person and occasionally gives copies of to his companions.

Various episodes, notably " The Sound of Drums ", also note that the TARDIS generates a perception filter to reinforce the idea that it is perfectly ordinary.

The TARDIS proves to be no ordinary police box: when Ian and Barbara enter, they discover it to be much bigger on the inside than the outside, and furnished with futuristic-looking controls.

Vansell's TARDIS arrives on Gallifrey but nothing is out of the ordinary, and he departs.

The revived series uses the Yale key version, most notably shown in " Blink " ( 2007 ), when the Weeping Angels attempt to gain access to the TARDIS using a stolen key.

The key is also able to repair temporal anomalies and paradoxes, including death aversion through its link to the TARDIS.

Upon pointing his key fob at the TARDIS, the TARDIS makes a distinctive chirp and the light on top of the TARDIS flashes.

Later in the same episode, the key fob, when again used by the Doctor, shifts the TARDIS " just a second out of sync " ( one second into the future ), rendering it invisible and so hiding it from the Master.

The Doctor attempted to use the TARDIS key in conjunction with a small electrical charge to recover the ship, but the process was interrupted and the TARDIS was only restored after the paradox was resolved.

It can, however, be opened with the Doctor's TARDIS key.

Lee steals the Doctor's possessions, including the TARDIS key, and runs off.

Meanwhile, Lee has returned to the TARDIS with the key, and entered the time machine.

The novel also states that the Doctor returned to recover Susan's discarded TARDIS key.

The Doctor thanks them and heads into the police box-followed by Ben and Polly, who enter the TARDIS with the intent to return Dodo's key, which the Doctor dropped earlier.

The Doctor disrupts the tunnel using the TARDIS key.

Finding the TARDIS locked, the Doctor manages to discover the key in one of his boots.

* The regenerated Doctor discovers the TARDIS key hidden in one of his shoes, this is a reprise of the same plot device that was used in Spearhead From Space.

Afterward, Ben and Polly are the bearers of the news of Dodo's decision to stay in 1966 to the Doctor, and accidentally get carried away in the TARDIS when they try to return Dodo's key to the time machine.

They are the bearers of the news of Dodo's decision to stay in 1966 to the Doctor, and accidentally get carried away in the TARDIS when they try to return Dodo's key to the time machine.

The Doctor enjoyed using his hat, umbrella and the TARDIS key, amongst other items, as physical props, usually as showy affectations or to command attention, while the umbrella could also be used to disarm and trip foes ( Paradise Towers, Battlefield, Ghost Light, Survival ).

Vyon then spots the Doctor leaving the TARDIS, and takes the key from him at gunpoint.