In this exclusive extract from Sara McCorquodale's book 'Influence: How social media influencers are shaping our digital future', McCorquodale explores her path to working with influencers and setting up her agency, CORQ, as well as the relationship between brands and influencers.

The questions that had started to form in my head were these: do we have any reason to believe people with large social audiences have the power to influence their audiences beyond their number of...