PMQs was going nicely with Labour bulldog Ed Balls snapping at the PM's heels, when a quip was too much for the shiny-faced premier.
Mentioning Britain's hard-won credibility on the back of the Coalition's cuts, Dave snipped as Ed bit hard into the Tory toff's ankle: "Which we wouldn't have if we listened to the muttering idiot sitting opposite me."
There was a loud roar but it was difficult to discern which side was shouting the louder.
It was tweeted that Mr B had unnerved the PM by urging him to "chillax, have another glass of wine" – a reference to the recent revelation that our noble leader unwinds with a game of tennis, a glass of wine and a spot of karaoke.
For his part, the Shadow Chancellor later noted how he had simply goaded the PM by urging him to "tell us about the recession".
As the Commons roar subsided Speaker Bercow – another parliamentarian Flashman holds in low esteem – pointed out how the word idiot was unparliamentary and asked Dave to withdraw it.
Flashman duly obliged saying he would replace it with the words "the man who left us with this enormous deficit and this financial crisis".
Of course, this is not the first time the Tory toff has vented his spleen.
Among his memorable barbs was telling Labour frontbencher Angela Eagle to "calm down dear", describing Tory backbencher Nadine Dorries as "extremely frustrated" and branding Labour veteran Dennis Skinner a "dinosaur".
Previously, the PM has likened the muttering Mr Balls as like "having someone with Tourette's sitting opposite you", a remark he later apologised for.
Later, Flashman was again in apologetic mode when he said sorry to the Beast of Bolsover for likening him to a brontosaurus and insisted he really regarded him as a "tremendous ornament to this House" – like grandma's cracked old aspidistra perhaps?
Lord Lamont, the former Tory Chancellor – whom Dave worked for all those years ago on Black Wednesday – noted: "He can be quite volatile - That makes him more engaging."
Volatility? Prime Minister? Surely not?