Election 2015: Will the Scottish National Party shake up the election?

As polls suggest there may be a hung parliament after the general election of 7 May, attention is turning to the likely influence of the smaller political parties.

SNP leader Nicola Sturgeon is widely thought to have given an impressive performance in a TV election debate on Thursday night.

Scotland correspondent James Cook went out with her on the campaign trail to see what effect the SNP might have.