When Patrick Mercer met a fictional lobbying company, Alistair Andrews Communications, and agreed to take money to work on behalf of business interests in Fiji, why didn't he think: "Hmm, I wonder if this extremely fishy-sounding operation is real, or one of those now all-too-familiar stings that have nailed so many of my colleagues"? And that awful quote: "I do not charge a great deal of money for these things. I would normally come out at £500 per half day. So £1,000 a day." Why was Mercer not reminded of the words of Stephen "cab-for-hire" Byers, when he was stung, in a remarkably similar way, by the very same journalist working with Channel 4 Dispatches in 2010?
Mercer has resigned from the Conservative Party and referred himself to the Parliamentary Commissioner for Standards following the investigation by BBC Panorama and The Daily Telegraph. A former holder of this post, Alistair Graham, has described the MP's actions as "parliamentary prostitution", and he is quite right. If Patrick Mercer has an ounce of principle he should stand down as an MP immediately.
Patrick Mercer has been a fool. His concept of what constitutes "not a great deal of money" is distasteful. But he and other politicians like him are an easy target. This is not to diminish the work of the journalists behind this investigation – an easy target is still a legitimate target, and every individual elected to represent us needs to be held to account. And yet lobbying is what happens. It is legal, and it is no surprise that people can make money from advising clients how best to put their arguments to parliamentarians.
Imagine if Patrick Mercer had set up his all-party parliamentary group (APPG) on Fiji because he had grown up there, or had a passionate interest in the plight of Pacific islanders. Is that really what an MP is for? Perhaps it is. Would our democracy be better served if the MP for Newark had stuck strictly to the concerns of the people of this East Midlands market town (or any Fijian businesses are based there)? Probably not.
Patrick Mercer lost sight of his duty as an MP. But his personal catastrophe was, in part, the consequence of a wider crisis in our relationship with Parliament. It is likely that these latest revelations will increase the pressure for the statutory register of lobbyists promised by the coalition. It is certainly the case that the APPG system is open to abuse and ripe for reform. But, in the end, this is isn't about defining what a lobbyist is. It is about defining what an MP is.
Martin Bright is former political editor of 'New Statesman' and 'Jewish Chronicle'