As Derek's finger pressed down on the button, the whole of the TARDIS lurched to the left side, and, grasping rather fiercly at an edge of the console, it was all the Doctor could do not to tumble and fall off.
So much for a simple prove-your-point. How did he get them into this? The Doctor's eyes went back to the monitor instantly, watching the blip flicker into and out of existence.
"It's moving, switching timestreams, almost got it!"