The TARDIS Key

Just as the TARDIS has changed over the years, so too has the key. The first key was a simple 'Yale' type key (similar to one used by the BBC Radiophonic Workshop to create the TARDIS dematerialisation sound). The 'Yale' style of key was used until The Green Death, and featured on screen several times in the series.

The Doctor used the key and chain to short out a control panel in the Dalek city in The Daleks. Two stories later, in Marco Polo, he was able to make a replacement key in the TARDIS workshop when he had to surrender his own to the Venetian explorer.

Susan threw her key away in The Dalek Invasion of Earth, but the Doctor made another which appeared in The War Machines - it was found by Ben, and he and Polly used it to enter the ship at the end of the story.

In Spearhead from Space the Doctor told the Brigadier that the key was tuned to his molecular pattern so only he could open the TARDIS door. The Doctor kept the key in his shoe.

This 'Yale' style of key was not only used by the Doctor; the Master's TARDIS in Terror of the Autons and Colony in Space was also accessible with one.

The Time Warrior saw the debut of the new TARDIS key. This was a semi-circular spade-shaped affair with one side featuring a series of raised triangles. The Doctor generally wore this around his neck on a chain, although in Robot the newly regenerated Doctor found it in his boot.

In Pyramids of Mars the Doctor threw the key into the space/time tunnel and it came out undamaged proving that it was made of a special material. Sutekh was able to teleport the key back through the tunnel in Part Four.

In The Android Invasion the Doctor left the key in the TARDIS lock, deactivating the pause control which sent the ship to the real Earth.

This 'spade' key lasted until the end of Season Thirteen. It was discarded when the new police box prop was built for Season Fourteen. From that season until Season Twenty-Five a 'Yale' key was once again used.

In The Deadly Assassin and The Invasion of Time, the TARDIS was forced open by the use of cypher-ident keys. In the latter case this was a large disc of red plastic with a 'Yale' style blade.

The Doctor carried a spare key which he gave to Adric in Four to Doomsday and this seems to be the only incident of there being a spare during this period.

In Part Three of Ghost Light the fourth key made its one and only appearance. This one had a flat angular fan shape with a circular head engraved with the Prydonian seal symbol. A photo of this appeared in Doctor Who Magazine 176.

The TARDIS lock itself was revealed to have a few special properties during the First Doctor's era.

In the pilot episode the Doctor pulled the whole lock mechanism out before the door could be opened. While this feature was not used in the remount of the episode, in The Sensorites the creatures removed the entire lock chamber, preventing the travellers getting into the TARDIS.

In The Daleks, Susan explained to Ian and Barbara that the TARDIS lock had a special defense mechanism. There are twenty-one different holes inside the lock; there is one right hole and twenty wrong ones. If the wrong hole is selected then the whole inside of the lock would melt.

In both The Web Planet and The Daleks' Master Plan the Doctor used his ring to open the TARDIS doors. In the latter story, the Meddling Monk melted the lock (presumably by using one of the wrong holes) and the Doctor used his ring to bypass the system. Later in Egypt, the Doctor effected repairs to the lock but the twenty-one-hole defense mechanism was not replaced.