Never again.
In all his one thousand centuries, the Doctor had parted ways with many dear friends, but he had only ever truly lost one.
Whether he forced them to go, for their own sake…
Susan… Sarah Jane…
Whether they were torn from his grasp…
Zoe…Jamie…
Whether they left of their own will, the strain too much to bear…
Tegan…oh Tegan…
Whether they stayed behind, to make a better life, and left him with a strange sense of pride…
Nyssa…Melanie…Ace…
Goodbyes were always painful. But one moment frozen in time had haunted him since his fifth life. And he had sworn, never again.
Never another Adric.
Slowly he slipped the yellow transportation disk from his pocket, testing its weight in his hands, brown eyes trained on Rose's long blonde hair. Listened as Jackie tried to reason with her to come with them. Watched as Rose reassured her that she would be alright if she stayed behind. The Doctor would protect her. Yes he would.
I'm sorry Rose. But I can't let you die.
He caught Pete's eye, nodded subtly, and slipped the chain around Rose's neck. Before she could react, Pete had depressed the button, and Rose's startled and betrayed expression vanished with the rest of them.
The Doctor faced the empty room for only a moment before moving into action. Whatever happened, he had made sure she was safe. And he had work to do.