Chronotis's TARDIS

Professor Chronotis' TARDIS was disguised as his rooms at St. Cedd's College at Cambridge University. It was capable of holding another TARDIS within its force field and of creating a bridge between the two to walk through.

Chronotis' model was a much earlier version than the Doctor's Type 40, and as such could interfere in an individual's time stream. It was stated that it was a type 39 TARDIS. (DW: Shada, WC: Shada, BFA: Shada).