The Doctor slipped a small pack out of his pocket.
He looked at it, then did a double-take. "Nitro-9?!"
His lips compressed.
"Damn. I can't possibly use this. Ace..."
He glanced over at Rose. Grinned.
"I suppose I can claim self-defense for this."
He pressed some buttons on the pack, then tossed it in the direction of the group of Cybermen, then ran, dragging her behind.
As they ran, Rose was berating him. It didn't wipe the grin from his face, somehow.
"Doctor, you killed them all! I thought you had changed!"
The Doctor paused a moment, fiddled with the knobs on the TARDIS as Rose closed the doors. On screen, a curly haired man in an improbably-coloured coat struggled with a pair of Cybermen... still very much alive.
"Like I said, Rose." He turned and smiled at her, relief showing on his face. His hand stabbed down to erase the image on-screen. "Self-defense."