Elsewhere, the Master had a Type 45 TARDIS with the ability to take control of other TARDISes, and the Monk had a Type 40 Mark IV, which was more advanced than the Doctor's. ...

The Doctor's rather unreliable type 40 TARDIS appears as a Police Box - but only because the chameleon circuit that allows the TARDIS to appear in any form got jammed on earth in 1963.

The story of Doctor Who from the BBC Archives: An exploration of the TARDIS, a Type 40 Capsule that transports the Doctor through time and space.