The Conservatives in Westminster and the SNP in Scotland are riding on waves of success – the 2015 general election result handed them political dominance in their respective regions.

The SNP, which is holding its conference in Aberdeen, is stronger at Westminster than any Scottish party has ever been; Labour at its peak could not match the proportion of 56 seats out of 59.

But what are the problems that come with this success?

Today presenter James Naughtie brought together two political heavyweights - Alastair Campbell, Tony Blair's Director of Communications and Strategy, and Kenneth Clarke, Conservative Chancellor and a minister in many jobs for 23 years – to discuss how successful politicians best avoid the lure of over-confidence.