Temporal grace

Temporal grace was the term used to describe the state in which the interior of TARDISes existed. Supposedly, it ensured no weapons could be used inside the Doctor's TARDIS. (TV: The Hand of Fear, The Invasion of Time) However, on many occasions, it seemed that no such defence existed. Cybermen (TV: Earthshock, Attack of the Cybermen) and a Dalek (TV: The Parting of the Ways) discharged their guns in the TARDIS. Nyssa presumed the grace broken when the Cybermen fired weapons inside the TARDIS. The Fifth Doctor replied, "Nobody's perfect." (TV: Arc of Infinity) Later, the Seventh Doctor said that the State of Grace circuit still needed looking at. (PROSE: 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 lie". (TV: Let's Kill Hitler)