How democratic is the interest group process in the UK?

Between elections, the interest group process (along with media and social media coverage) is a key way in which citizens can seek to communicate with their MPs and other representatives, and to influence government policy-makers. For the 2018 Audit of UK Democracy, Patrick Dunleavy considers how far different social groups can gain access and influence decision-makers. How democratically does this key form of input politics operate? And how effectively are all UK citizens’ interests considered?