"We are trying to humanise the politicians," Walker says.

"Usually they are staring down the barrel of the camera or pulling a nothing 'powerful' face. This took it to a different level."

The question was, how to elicit emotion from politicians who are as practised at posing as they are at reciting slogans? And during an election campaign when the politicians (and their teams) obsessively control their own images?

Walker hit upon the idea of showing his subjects photographs of people or things that would elicit an emotional response.

He used a tele-prompter to flash the politicians images of their children and grandchildren, their partners and their political nemeses, both from the other side and from within their own parties.