Last year's general election should have been an easy result to predict. There was a constant stream of opinion polls, many more than in previous campaigns. But they turned out to be highly misleading, suggesting a hung parliament. The actual result was a huge shock to the polling industry. So went wrong with the polls, and why? And how easy will it be to put it right?

In the final part of a series examining the role of opinion polling in British politics, David Cowling asks if polling will be more reliable in future and if the industry can restore its reputation in the wake of its errors at the last general election.

Producer: Martin Rosenbaum. Show less