(http://media-cache-ec3.pinimg.com/736x/b2/5c/02/b25c021a11f167e25271977630681025.jpg)
Graham and the Doctor? yes please :P
Graham: Explain to me again - why can't we just go back in time and prevent the whole thing from happening?
Wibbly-wobbly, timey-wimey reasons ;)
Because then something even WORSE might happen otherwise no matter what you do?
Because we wouldn't have an episode then :P