© Provided by The GuardianPhotograph: House of Commons/PA
One of Keir Starmer's best gags - and the Labour leader could certainly do with a laugh this week - was describing David Cameron as "a former prime minister and now I suspect a former lobbyist".
Appearing in front of committees of MPs on Thursday, Cameron suggested that, indeed, his lobbying career was behind him.
There were few moments of comfort for the prime minister. He was asked about how much he earned, but he wouldn't say. He was asked about how much he knew about the precarious state of Greensill as he frantically lobbied ministers and officials. Not a lot, he suggested.
© Photograph: House of Commons/PADavid Cameron giving evidence to the House of Commons Treasury committee on Greensill Capital.
Hearing the way Cameron operated highlighted the key question MPs and public inquiries must grapple with over the coming months: how can such a scenario can be avoided again?
The culture of "a quiet word in your ear" that Cameron decried in a speech them decade ago is clearly thriving in Westminster.
In his evidence, Cameron mounted some defence of the current system of regulation, while accepting that it could have been improved, citing the lobbying reforms which he undertook as prime minister.
What he neglected to mention was that the revelations about his conduct did not come about because of disclosures on his lobbying register - which he was exempt from anyway - but because of investigative journalism. That fact alone suggests the system is not doing its job in discouraging the kind of behaviour Cameron engaged in.
Related: Timeline: David Cameron and Greensill Capital
Cameron was not entirely in defensive mode. He conceded his 59 frantic messages to senior politicians and officials might have been better off as a formal letter. And he did suggest there was a case for a longer period of respite before an ex-prime minister should be able to contact government.
But he said it was not quite right that contact should be barred entirely and suggested, almost wistfully, that a former prime minister could be approached to chair a big bank or British company, in which capacity they would need to contact government.
More salient perhaps was when Cameron pointed out he is a relatively young ex-prime minister, though there will be few who shed many tears when he said he did not want to sit on a board and make a few dinner speeches. He wanted "to get stuck in and help a business grow and expand" - read: make money.
There will be ex-prime ministers in the future who also leave office while relatively young and still ambitious. A system must be fit to deal - at some point in the future - with Boris Johnson when he departs No 10, a red team test if there ever was one.
But there are some relationships that it will always be hard for systems to account for - friendships that exist between former colleagues, such as the one which got Matt Hancock into hot water when he accepted an invite for a drink with his old boss, Cameron, who invited along his mate Lex Greensill.
In many ways, the key problem was revealed by Harriett Baldwin who, in an exchange of teeth-grinding awkwardness, asked why had he signed off messages to the Treasury permanent secretary, Tom Scholar, with "Love Dc".
That exchange seems chummy for what was essentially a business discussion, but Cameron said it was how he signed off every text. Except he did not sign off messages to others, such as Rishi Sunak or Michael Gove, with that greeting.
Scholar and Cameron are former close colleagues and by Cameron's account the pair have met socially, albeit, he said, only twice in five years. Cameron conceded that signoff was because he knew Scholar far better.
The past year has shown - including with the scandal over PPE contracts - how quickly in times of crisis politicians turn to their mates, because they are people they trust to provide answers or advice.
Cameron's evidence underlined still further how important it is to have a system that guards against abuse of personal relationships, especially when one side potentially has millions to gain.