Every now and then, we get to see the cogs, pulleys and lubrication of the hidden machinery of global deal-making. We saw it when Peter Mandelson's friend Nat Rothschild told tales about conversations that George Osborne denied having on Oleg Deripaska's yacht. And we saw it last week when Liam Fox resigned because he had solicited donations to a secret outfit "involved in security policy analysis andresearch", which had paid forhotels and travel for his friend Adam Werritty.

Anyone not following the story closely – and that could be excused – might have been puzzled as to what it was that finally prompted Mr Fox's resignation. The story of Mr Fox's friend, who seemed to have a curious habit of turning up in the same hotel around the world as the Defence Secretary, but who did not travel "with" him, had been running for some time. Mr Werritty's role was first reported in August, along with his practice of handing out business cards describing himself as Mr Fox's adviser. And, for the past two weeks, Mr Fox has featured on the front pages nearly every day. However, as Mark Felt, " Deep Throat", advised at the time of Watergate: "Follow the money".

It was the question of who paid for Mr Werritty's travels that finally required Mr Fox to take responsibility. It was the discovery on Friday that several donors, some of them with interests in defence and security, had given money to a non-profit group called Pargav that prompted Mr Fox's departure. Pargav seems to have allowed Mr Werritty to function as a cross between a security consultancy; a shadow foreign office running a shadow foreign policy notably aggressive towards Iran; an ideological think-tank; and a future Tory leadership campaign. How much of that was fantasy (and in that case, whose?) and how much was serious power-broking and money-making is hard to tell.

The main reason that it was, and remains, hard to tell is because Mr Fox did not disclose the financial interests that surrounded his office. This ought to be a useful corrective to some of the enthusiasm for transparency that has become a little misdirected recently. While some MPs have seen the fall of the House of Murdoch as an excuse to demand a log of every journalist with whom Nick Clegg has had lunch, we ought to remember that the main need for transparency is in shining a light on the personal and financial interests that surround ministerial and official decisions.

What is so extraordinary about Mr Fox's case is that he thought either that the donations would never become public or that it would not look bad if they did. In that light, we should acknowledge that his resignation shows the British political system working as it should. At a time when the reputation of journalism has been dragged through the mud, we should celebrate a free press tenaciously pursuing the relationship between Mr Fox and his non-adviser.

And we should acknowledge that the Prime Minister handled the allegations well. He asked civil servants to gather the facts and to allow Mr Fox to explain himself. It was suggested that this allowed the Prime Minister to act as judge and jury, but it achieved the right result, and did not preclude a formal investigation by an independent authority later. David Cameron's cool respect for due process reflects well on him. (Mr Cameron's reluctance to move ministers, and his limited reshuffle after Mr Fox's resignation, are also to his credit.)

That said, we are left with the suspicion that Mr Fox's jaunty attitude towards ministerial propriety is not an isolated example. Indeed, Mr Cameron, for all his political skill and admirable sang-froid, has shown a somewhat "who, me?" insouciance about the possibility of conflicts of interests about his leadership. The idea, for example, that he had no doubts about Lord Ashcroft's tax status while the peer was deputy chairman of the Conservative Party is implausible. Mr Cameron seems to someone who thinks that he knows how the world works but wants to be kept at arm's length from the grubby details.

In opposition, in February 2010, he said that lobbying, "the far-too-cosy relationship between politics, government, business and money", was "the next big scandal waiting to happen". We cannot rely on him to ensure that it does not. It is up to a vigorous and confident press to hold the Government to the standards of transparency that it, erratically, professes.