"Can't know about until the time is right?" Her look turned cross, not overly but still there. "You do realise that I live in a time machine right now, don't you? I would imagine something like time would be irrelevant."

Besides, why couldn't she or the Doctor know about it? It wasn't as if they would try to change anything, oh no. Sarah knew the Doctor well enough that he wouldn't go on some idealistic crusade unless he was dragged into it.

So what was the problem then?