Something odd happened at the Guardian on Monday as the paper’s editorial staff were basking in the glow of their just-published splash about the Panama papers. They were understandably excited, having sat on the revelations for months, and were about to put flesh on the bones of the stories that had broken on Sunday evening about the elaborate tax-avoidance schemes of assorted Tory bigwigs. The Guardian was one of 107 media organisations that had been secretly going through the cache of 11.5 million documents stolen from the Panamanian law firm Mossack Fonseca last August and these were the golden nuggets: disclosures guaranteed to cause the government maximum embarrassment and — an added bonus — give a much-needed boost to Jeremy Corbyn. With a bit of luck, the paper’s associate editor Seumas Milne, who is widely disliked on the editorial floor, would remain on secondment to the Labour leader’s office for some time to come.

But even allowing for all that, what happened next was still perplexing. They gave themselves a round of applause. That’s right, the Guardian’s editorial staff put down their cups of fair-trade coffee and started clapping. In their eyes, these revelations about the use of offshore tax shelters by various grandees were a cause for self-congratulation.

Now, I can think of three possible explanations. First, they either didn’t know or had forgotten about the Guardian Media Group’s use of a tax-exempt shell company in the Cayman Islands to avoid paying corporation tax when it sold its 50 per cent holding in Auto Trader to Apax Partners in 2008 (hat tip to Guido Fawkes). Further, they were similarly ignorant about the hundreds of millions GMG has invested in offshore hedge funds over the years. But that seems unlikely. After all, right-wing hacks like me lose no opportunity to draw attention to the paper’s creative tax affairs, particularly when confronted with self-righteous columnists like Owen Jones and Polly Toynbee wagging their fingers at Vodafone and Starbucks for avoiding paying their ‘fair share’.

A second possibility — and, admittedly, this is farfetched — is that the paper’s hacks have actually read and been convinced by the former editor Alan Rusbridger’s long, rambling explanation of why the directors of GMG aren’t tax-dodgers after all. In his 2,000-word essay on the subject, published three years after the allegations were first put to him (so much for transparency!), he claims it was perfectly right and proper that GMG didn’t pay a single penny in corporation tax on its £302 million profit from that sale. Insofar as I understand it (and I’ve read it three times) the gist of Rusbridger’s argument is that GMG’s tax affairs are all fine and dandy because they’re perfectly legal. Hmm. Couldn’t exactly the same defence be made of the Tory bigwigs?

No, the correct explanation, I believe, is that the paper’s hacks were applauding the sheer brazenness of their hypocrisy. This wasn’t common-or-garden two-facedness, like attacking the government’s decision to give council-flat tenants the opportunity to own their homes while owning two or three yourself. Or pouring scorn on free-school founders desperately seeking an alternative to sink comprehensives while sending your own kids to a top public school. No, this was hypocrisy on an audacious scale.

When those Guardian journalists thought about the Panama stories, they must have experienced the thrill felt by the televangelist Jimmy Swaggart as he railed against adultery from his pulpit having just slept with a New Orleans prostitute.

Even more deliciously, the charge they level at the Prime Minister — financially benefiting from a tax arrangement he had nothing to do with — is one they were all guilty of themselves. After all, the Guardian would have long gone out of business without the financial fleet-footedness of GMG’s directors. And on top of that, the icing on the cake, they were holding a leading politician responsible for the alleged sins of his father, something many of them condemned in a fit of high dudgeon when the Daily Mail ran its story about Ralph Miliband in 2013. What larks! This was the hypocritical equivalent of a triple word score. In for a penny, in for a pound, and no tax payable on the winnings thanks to GMG’s fiendishly clever offshore tax arrangements.

On reflection, I’m amazed the Guardian hacks don’t give themselves a round of applause every morning.