Chief Executive of the Advertising Standards Authority, Guy Parker is responsible for regulating advertising in the UK. In this in-depth one-to-one interview, he explains the challenges the ASA faces regulating the web and YouTube; describes the behind-the-scenes process that goes into deciding whether an advert is offensive or not; and explains the rationale of its more contentious rulings, including on the Atheist Bus Campaign and the 'Are You Beach Body Ready?' posters.