Temporal grace

Temporal grace was a term used to describe the state in which the interior of TARDISes existed. Allegedly, it ensured that no weapons could be used inside the environs of the Doctor's TARDIS. (DW: The Hand of Fear, The Invasion of Time) However, on other occasions, it seemed that no such defense existed. Cybermen (DW: Earthshock, Attack of the Cybermen) and a Dalek (DW: The Parting of the Ways), for example, discharged its gun in the TARDIS. Nyssa presumed the grace broken when the Cyberman was able to fire weapons inside the TARDIS. The Fifth Doctor replied, "Nobody's perfect." (DW: Arc of Infinity) Later, the Seventh Doctor said that the State of Grace circuit still needed looking at. (NA: Cat's Cradle: Time's Crucible) After Mels shot the TARDIS console, the Eleventh Doctor admitted that the presence of temporal grace in the TARDIS was (at least at that point) a "clever line". (DW: Let's Kill Hitler)