Protection of wildlife and the countryside has long been a popular issue in Britain, and the subject of active lobbying by interest groups. By contrast, pollution has attracted much less public attention. There are two reasons for this. First, the most visible form of air pollution - smoke - was addressed by the 1956 Clean Air Act. Other forms of air pollution have remained, and in some cases grown worse, but few are as visible as smoke. Secondly, and more importantly, the limited public interest in pollution issues, and the low level of opposition or public mobilization on the part of environmental groups, is due to the fact that Britain's pollution control has traditionally been based on a policy of non-coercive, voluntary compliance, and a "partnership" between the regulators (central and local government) and the regulated. Unlike planning decisions, which can be very public and visible, pollution control policy has been shrouded in secrecy.