Mr Cameron tried to embarrass Mr Brown over his tense relationship with Mr Darling in thepast but did not quite make the case that it mattered for the present.
When we look at that environment, that ecological niche if you like, we found (past tense, for of course all of these models are up in the air now) that in different parts of the environment different models worked.
Future, active, pasttense questioning helps to paint the picture of success between the individuals involved, often uncovering expectations that would otherwise not see the light of day.