A/N: WARNING! Contains spoilers for series 4! A bit melancholy, but I felt like writing it.
Alone
Sir Doctor of TARDIS, last of the Time Lords, man from Gallifrey, defender of time. The TARDIS was empty once again, lights dimmer than usual. There were times when he just wished he could settle down, like when he tried to save the Master on the Valient, or after he lost his Jenny. But it never could be. It never could happen. He lived for excitement, for the danger of adventuring around the universe in a little blue box. And even if he wanted to settle down, it wasn't possible. The universe needed him. When the Time Lords were still alive, when Gallifrey was still in the heavens, he would have been able to, but not anymore. The Time Lords had kept the universe safe, made sure that everything worked as it should, and with them all gone, that task fell to him.
Sometimes he wondered whether it was worth t, whether continuing to travel was worth all the heartbreak. Losing the Time Lords was one thing, but losing everyone he travelled with was something else. There was Rose, trapped in a parallel universe. Martha, gone because he didn't take any notice of her. Donna, his fiery independent Donna, memory wiped by him, back to how she had been before he had met her. There was no one now. No one for him to go back to; all his friend had their own lives to be getting on with. The TARDIS was the one companion that would never leave him.
The scanner beeped at him, flashing a dangerous mauve. The Doctor watched as the heavily armed warship streaked down towards the planet below, locking onto Cardiff. "Here we go again," he muttered to the silent room, "let's go save the world."
He released the handbrake with a certain amount of reluctance.