The Tourist nods, "Most folks who try to change the past become part of history and end up ensuring the event they want to change does come about."
Brooklyn nods, "Goliath said you can't change the past, it is immutable."
The Tourist nods, "for most, but Time lords, and some others can change the past, though you get in severe trouble if you try and the council sends out certain agents like myself to unchange or / and ensure what happens is what should. There there have been rumours of a few exceptions being made." He nods to what Merlin said, "We have a special relationship with time. Part of it is overseeing time. I don't know the fullness of the details. I wonder if even the lord president does. Maybe only Rassilon does, or did." The tourist said.