Lying is rather frowned upon in the House of Commons. Indeed it's assumed that since no MP, honourable as he or she is, would stoop to such levels, it's deemed unparliamentary language to even accuse someone of being a liar.
Blackguard, git, guttersnipe and other vicious slurs are also on the banned list, but they were less on David Cameron's mind on Wednesday when he ridiculed the prime minister. "If a company director got up and read out a statement like that, the authorities would be after him," said the leader of the opposition - that's "Gordon Brown's a liar" to you and me.
And you and me probably wouldn't be that shocked if MPs did lie - after all the popular approach to politicians is perhaps best summed up by the "Why is this lying bastard lying to me" school of thought beloved by some journalists. It's unfair of course, but the age of spin and selective use of stats has left many voters rather jaded.
So what a delight when a politician is brazenly, shockingly, in-your-face honest and decides to tell it like it is. The former Education Secretary Estelle Morris who resigned when she realised she just wasn't good enough, the late Alan Clark who gabbled through a ministerial speech on equal pay and "found himself sneering at the more unintelligible passages", startled by the "sheer odiousness of the text". And now, as highlighted by the Politics Show this week, Mike Russell.
Mr Russell is the environment minister in the SNP administration at the Scottish Parliament. Called a few days ago to make the closing speech in a debate on "Moving Scotland Forward", custom and courtesy might have expected him to praise the previous speakers or applaud the quality of the contributions. Thankfully for us, not a bit of it. He told a wide-eyed Parliament that the debate had been pointless, uninteresting and useless. It was political theatre. And, gloriously, he declined to take any interventions from other MSPs on the basis it would waste everyone's time still further, adding: "My intention is to get through this and then I want to go home".
Does this make it into the top ten most honest political moments? It would be an interesting list - if a tad short, you might fear. "It is appropriate for ministers to tell the truth and that's what I intend to do," said the candid Mr Russell. The only worrying thing for us voters is that a politician feels he has to spell that out.