He looks around the Citadel, enjoying one final moment of peace before leaving for the war. TARDISes are everywhere, left in the owner's preferred disguise. There was the Rani's glass pyramid, and the Corsair's space vessel.
Someone is coming towards him from the far side of the hall, weaving through the parked TARDISes to the one stuck as a 1963 police box. A woman, still in her first regeneration, younger than he was when he left Gallifrey so many years ago, walks up to him. "Grandfather? Grandfather, it's me. Susan."
"I said I'd be back—" he hugged her tightly.