Type 12

Type 12 was a type of TARDIS used by Time Lords.

It was a much older model than the Doctor's Type 40 TARDIS. Professor Chronotis owned a Type 12 Mark 1 TARDIS, which served as his rooms at St Cedd's College, Cambridge. This TARDIS model could hold another TARDIS within its force field and create a bridge between the two to walk through. Type 12 TARDISes were capable of interfering in an individual's time stream. It either did not have a chameleon circuit, or his didn't work. (PROSE: Shada)

Behind the scenes

 * The model of Professor Chronotis' TARDIS is not mentioned in the script book or the surviving footage from Shada, nor in the webcast or audio versions. In Gareth Roberts' 2012 novelisation, the Doctor identifies it as a "Type 12, Mark 1".