For most people sitting in Court 13 of the Royal Courts of Justice, it has been an educational experience watching motor racing boss Max Mosley attempt to sue the News of the World for grossly invading his privacy.
We have learned that after whipping each other until they bleed, devotees of sadomasochism (S&M) like to put the kettle on and have a cup of tea, and that despite her husband practising S&M for 45 years, Mosley's wife apparently never noticed the bruises. And who knew that the plural of dominatrix was dominatrices?
Yesterday came the opportunity to gain specialist knowledge of a rather different, but no less fascinating, kind: how a tabloid newspaper functions.
The first witness called for the defence was Colin Myler, the News of the World editor. One of his most interesting admissions - to anyone who may ever be tempted to sell a story to his newspaper, at least - is that informants very rarely receive the money they are promised in the early stages of an investigation.
James Price, Mosley's QC, suggested to Myler that the real reason the paper's mole ("Woman E", the dominatrix who secretly filmed what the paper later described as the "sick Nazi orgy") didn't receive the £25,000 she was originally offered was because the footage was rather disappointing - there simply was not enough "unmistakably Nazi" stuff in there.
Not so, according to Myler. "Every fee is renegotiated ... we negotiate just as in any other business deal," he said, adding with a flourish: "We are in a credit crunch, Mr Price." Woman E eventually received £12,000, less than half the pledged amount.
It wasn't a vintage performance from Myler - who, Price was delighted to remind him, has form in the invading-of-privacy department. Hadn't Myler caused "something of a furore" while editor of the Sunday Mirror in 1993 when his newspaper hid a camera in Princess Diana's gym and printed pictures of her exercising? Myler was forced to concede on this point.
He had already been made by Price to look through 93 stills of the "orgy", and was asked a rather tedious 93 times whether he could see anything unmistakably Nazi in what he saw. With wearying regularity he sighed and gave a reluctant "no" each time, and could only pick out a few shots with women wearing striped uniforms, which, he said, had "concentration camp" connotations, or women in military garb.
He also found himself agreeing with Price's suggestion that it would have been "highly instructive" to have translated the film from German before publication. "In fairness to Mr Mosley," he said, "Yes."
Mosley maintains that he and the women were acting out a prison scenario, and that he and Woman B, a German, made repeated references to prison cells and life sentences - references the newspaper didn't pick up on because they were spoken in German.
Throughout this cross-examination, Tom Crone, the News of the World's legal manager, appeared increasingly agitated, rubbing his face in his hands. By the time the afternoon session rolled around he had reached for his handkerchief and was wiping his brow.
Myler admitted that he didn't personally authorise the use of a hidden camera on the Mosley story before his chief reporter strapped his dominatrix informant, Woman E, with a device and sent her to the Chelsea gathering.
Yes, he knew all about the Press Complaints Commission guidelines on the use of clandestine listening devices - that there must be a very good public interest in doing so, and that the information must not be gatherable by any other means - but felt there was enough of a public interest defence here.
Neville Thurlbeck, the NOTW reporter responsible for the Mosley exclusive, gave a rather more robust, if equally flush-faced, performance. He said there was absolutely no way of getting the story without a secret recording, justified because the "orgy" was violent to the point of illegality.
He added: "Because the sadomasochism was so graphically outlined, we took it for granted that there was a public interest justification."
Getting pictures of Mosley entering the flat after the five dominatrices wasn't enough. For all he knew, Mosley was going into the building "to fix the fusebox and have a cup of tea".
He denied that he was disappointed that there were no "Sieg Heils" or bits of out-and-out Nazism in the recording.
"I was completely surprised by the level of Nazism," he said. "I kind of suspected it might be some sort of watered down, comedy version of 'Allo 'Allo. But when we looked at the video it became clear very quickly that there was a very cynical Nazi theme throughout."
He pooh-poohed Price's observations that the "Nazi uniform" was in fact a modern-day Luftwaffe jacket and that the "concentration camp outfits" were joke-shop prisoner costumes. "This is am-dram stuff. Their wardrobe department let them down ... it's still quite clear what they are trying to mimic."
He added: "I don't know of any fancy dress shops that sell concentration camp uniforms."
Thurlbeck is due to finish giving evidence today, and is expected to be followed in the witness box by Woman E, the News of the World's informant.
· This article was amended on Friday July 11 2008. We asked, "who knew that the plural of dominatrix was dominatrice?" It isn't; it's dominatrices. We misreported a question put in cross-examination about translating some of the video into German; that should have been from German. And the name of the QC acting for Mosley is James, not David, Price. These have all been corrected.
