Early in 1972, I was working as a consumer researcher at the J. Walter Thompson ad agency in Berkeley Square, London. Although my main task was to test new commercials to check they were communicating effectively, from time to time I was asked to help with the odd casting problem: that is, creative groups occasionally asked if our Unit could assess the relative appeal of various actors in the running for a role in one or another 30-second epic.

I always felt ill-at-ease doing this. My experience over the years has been that consumers choose the bland ahead of the striking. But on one occasion, I was certain the research could help. This was when the Gillette client asked if I could do some filmed focus groups with members of the public who might feature in a new campaign describing how male shavers felt a double-blade razor helped them get a closer shave.

We’ve moved on a long way since then. Back in 1972, as Dick Nixon returned triumphantly for a second term, a razor with two blades was NASA moon-landing stuff. Gillette was locked in a battle with Wilkinson Sword to decide whose brand would dominate in the smooth-face sector of male hair removal. Given the market was shrinking at the time in favour of blokes who preferred hairy rock-star as a look, a continual increase in market share via continuous improvement of product quality was all shaving-product marketers cared about.

As part of this process, we had to design a sample recruitment questionnaire to ensure that 100% of those who turned up at the focus groups would be male, daily shavers, and likely to produce the best before/after shots of stubble being replaced by baby’s bum smoothness. During the discussion, the director pointed out that there was no point in looking at Afro-Caribbean guys, as their stubble wouldn’t show onscreen. So the recruitment agency we’d hired put a proviso into the questionnaire saying “Do not recruit black males”. Technically, this was an offence against the Race Relations Act, although none of us thought about it.

But one black activist and his girlfriend did. The lady concerned happened to be a recruiter working for the market research company, and on seeing this clause, she got her partner involved. He in turn went to The Guardian. After some discussion, they decided that she should deliberately recruit her boyfriend for the focus group, and see what happened. She also recruited a Guardian journalist.

They turned up in the last group I took, and although I was immediately aware of the black guy there was no point in embarrassing him and the other people by making a fuss about it. As it turned out, he was a very good respondent – but there was no way his stubble would’ve shown up on film. (Bear in mind that, in 1972, the vast majority of ads were still screened via black and white television). The focus group wound up, and as those who’d taken part filed out, I noticed the two men still firmly rooted in their seats. I repeated that the session was over.

“We’re not going anywhere,” announced the stony-faced journalist. As the door closed on the last of the group members, The Guardian reporter explained with a triumphant flourish who he was.

“Unless you can give me some pretty good answers,” he added, “You are all in big trouble.”

I confess that at this point my legs turned to water. Behind a one-way viewing screen in the room, a group of suits were already making frantic calls to the main JWT office saying we had an emergency on our hands. And yet, being a bit dim, I was still unclear as to what this was about. All I knew was that, to Guardian journalists, advertising was the South Africa of commerce – the very quintessence of evil. It wasn’t until the hack started quoting from the Race Relations Act that the penny dropped.

I was terrified by this point, but then the journalist asked, “Well, what’s your excuse?” Somewhere in my head, a switch flicked.

My excuse?” I asked, “What’s yours? This is a simple case of the law unwittingly producing a farcical situation.”

I explained the technical problem of filming stubble on black skin. It was greeted with sneers and snarls by the two men. I decided I’d had enough.

“Look,” I explained, “You’re wandering up a blind alley. Now you’re both here under false pretences, so before we get any more unpleasantness, I think it’d be a good idea if…”

“You handle the South African Wine Farmers’ Association account, don’t you?” asserted the hack.

This was a big mistake: as it happened, I handled it personally.

“We do,” I said, “because SAWFA has an integrated workforce policy, and has refused to back down to the Nationalist Government’s bullying”.

I then got the usual bollocks about collaboration with fascist regimes.

There is something I should explain at this point. In 1972, I was a card-carrying liberal, three years out of University and still seeing myself as in the vanguard of changing the world. Richard Nixon was the anti-Christ, and the Daily Express was a Nazi newspaper.  My main confusion in this episode was an inability to persuade a nice man from the harmless Guardian that he’d made a mistake. And then, to my relief, two JWT security guards arrived and firmly suggested the two men should leave.

It was late Friday afternoon, and although shaken I quickly forgot the incident. I was due to visit best friend Shaun up at Oxford, and my main concern was getting out of London before the Big Rush up the M40 started. As I jumped into my green Mark II mini 850 (BKU 351C) the last thing on my mind was the media.

Shaun and I visited a few pubs, shared an Indian, and then collapsed into a bed and the sofa respectively.

The next morning, my chum prodded me at 9 am.

“You forgot to mention you were famous,” he said in his usual dry manner, and plonked a copy of the Guardian on my head. The second lead in the paper said, ‘Top Adman denies racism charges’.

Over the last half-century, I have only ever been two things to The Guardian: ‘Top Adman’ (I was a junior researcher at the time) and ‘Brown on pills blogger’ in 2009.

This was the beginning of the end of my belief in The Guardian. Ever afterwards, I was wary of the innate bigotry of some of its journalists. Having already developed a healthy disbelief in Murdoch’s Times, I suppose one can trace the genealogy of my current opinions from this point. During the early 1970s, I grew up in all manner of ways.

I could end the story there, except that the effects of the Guardian’s stick being waved at the wrong end were pernicious. The recruitment company (a small business) found itself in crisis, largely because most of its recruiters were black women who took the Guardian piece at face value. Worse still, the Guardian OpEd was talking about handing over the details to the 1972 equivalent of the Crown Prosecution Service. The article was a travesty of the truth. Over the next few days I got calls from friends advising me to cleanse myself of the advertising business. The only grubby thing I wanted to be away from was the amateurish witch-hunt of this kind of journalism.

And then, three days in, the media lost interest in pursuit of other inaccuracies. There were no retractions admitting that the ‘story’ had been an incompetent confection from start to finish. I got a personal memo from JWT’s CEO Denis Lanigan thanking me for defusing ‘a potentially explosive situation’. Only my American section-head Judie Lannon (still a friend) was available to peel me off the ceiling and explain that I should view the episode as a learning experience.

In the soil of this poisonous harvest was the weed of Thatcherism able to thrive. Millions of people like me – holders of a candle for the unfortunate – got utterly fed up with Lambeth’s nuclear-free zones and fraternal greetings to Moscow, but no grit on winter’s icy roads. We all became pissed off with the liberal press inventing the fascist police State where there appeared to be only frightened coppers being brutalised by their experiences. Blokes like me – keen for female equality – found ourselves tired of apologising for having a dick.

There is a dimension of the Left-liberal mindset still stuck in that 1972 of my memory. Unfortunately, it has wrested back control of the Labour Party from the Mandelson-Blair drivel of 1997-2010. This – and the wandering cream wallpaper of LibDemism – has left constructive radicals like me with nowhere to go. Worse still, it provides no effective resistance to the amoral opportunism of Camerlot. But without this bitter learning experience, I wouldn’t have moved on to a fuller understanding of how things really need to change.