Ms Sarah O'Connor:

I can be very brief. We carry out two pieces of analysis. One is a post-campaign analysis, which is done in the immediate weeks following a campaign. It tells us the number of eyeballs that will be on a campaign, or what we call impressions. It will tell us how many people clicked on a link and watched a video through to the end. That is one piece of analysis we do. We do a secondary piece of analysis, where we work with IPSOS on tracking research in the months after a campaign. We look at how many people, unprompted, said they saw the ad. If people said they saw a particular ad, and say they definitely saw it, we then ask them how many times they saw it. We dig into whether the ad made them more likely to slow down, pay more attention or prompt a conversation with family and friends. We have tracked that over the course of the past decade, not only within a campaign but how a campaign performed against particular best-in-practice campaigns that we have run in the past. That is the structure we have at the moment. We also look at the bigger trends with the work Mr. Rowland's research team does.