“There’s a lot of things you need to get across this universe. Warp drive… wormhole refractors… You know the thing you need most of all? You need a hand to hold.”
In the vortex that lies beyond time and space tumbled a police box that was not a police box. The control room was empty. It was a spacious, brightly lit, chamber. It alone was too big to have fitted, into the battered exterior of the police box, and doors and passageways leading from it hinted at more inexplicable volumes beyond.
-Doctor Who: The Wheel of Ice