In that intensely surreal period between a General Election being declared and decided (politely known by political enthusiasts as 'the campaign'), reporters, pundits and psephologists find themselves in a frenetic limbo where knowledge and ignorance are often indistinguishable - though it is their job to persuade us otherwise.

The biggest question we want answering is always, 'Who's going to win?' But despite the increasing sophistication of opinion polling techniques, ...