Andrew Brown of The Guardian asks if the dramatic rise of ad-blocking software will undermine the commercial model behind most free news on the internet. He finds an industry in deep concern over the "Ad-blockalypse" - with these new programmes meaning that advertisers may refuse to continue to subsidise online news providers if consumers are now no longer seeing their online adverts. Can the industry persuade people to pay for what was previously available at no charge? And if not, can commercial online news services survive? Producer: Katie Inman.