In response to a Freedom of Information request asking for details of advertisers, including a breakdown of categories of advertisement on its network, Transport for London (TfL) has said: "we do not have a list of companies that advertise on our network or a breakdown of revenue received by company. We have contracts with partners, e.g. Exterion Media, who run our advertising estate for us. The partner deals with the brands, companies and sectors to sell campaigns and space."
Given you now operate policies such as the ban on junk food advertisements, will you consider asking TfL to collect and report data on the kinds of companies buying advertising space? This would be useful not just in monitoring the effects of your food policies (for example whether fewer food companies are buying advertisement space after the ban) but also in being aware of the number of adverts by fossil fuel and arms companies, for example, or the ability of non-profits and small businesses to access this resource.