Peter Grimwade said this quote

Don't interfere! The Doctor silenced her angrily. I cannot will my own destruction.

~ Peter Grimwade

Mawdryn stared at the Brigadier with such a look of pain and longing. For a moment the old soldier's mind went back thirty-five years to his first taste of action as a young lieutenant in Palestine, with his platoon badly shot up by terrorists, and he remembered the mangled conscript who screamed at the officer to take his rifle and kill him.

~ Peter Grimwade