Looking back, I should have seen it was a set-up, but they were smart. The caller introduced himself as Todd Lewis, a Los Angeles producer. His company, he explained, was making a film for a German broadcaster about the American south, in particular my home town Birmingham, Alabama.

The patter continued. Todd's company was called Amesbury Chase Productions, one of a group of four. He gave me their internet addresses – they looked legit. Would it be possible, Todd asked, to film some ballroom dancing?

I've always enjoyed dancing. I learned as a teenager – waltz, swing, tango, Latin – and now help run a large dance club in Birmingham. It's been good for me. At age 75, the exercise is great and, more importantly, it's how I met Brenda, my girlfriend of 10 years. It was agreed that Todd and his cameras would shoot a dance at the Vestavia Hills civic centre in a suburb of Birmingham on Monday 9 February. The people there are mainly in their 70s. I was there with Brenda, who's 64. Todd's operation was impressive. They turned up in a motorhome with four cameramen and a crew chief. There were also two front men, and one woman, all aged between 30 and 35.

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Our visitors were thoughtful. They'd taken along 100 or so 12in red hearts to put on the wood panel walls (it was a Valentine's event). Entrance to this dance is $5 (£3), but the crew paid that for the 110 people attending. All we had to do, they told us, was sign sheets of paper at a card table set up by the door. The generosity continued. They gave the man running the dances $300 and the band leader another $100. What nice people, we thought. All the while, though, they were drawing us into their game. After 30 minutes of dancing, a man who was obviously a performer appeared. He had short blond hair and two tufts near the front. He wore a sleeveless white shirt, black leather waistcoat and trousers, and 16in pointed gold boots. Oh, and a black tie. I've seen slim ties in my time, but this was a little hokey.

The man said he was Austrian and didn't speak English; occasionally he pulled out an English-German phrasebook. I now know this was Sacha Baron Cohen. Then the crew asked to put on their own music – probably on an MP3 player – to avoid copyright infringement, they said. It was lousy, a cross between an Argentine tango and swing. The "Austrian" started dancing with a second actor who'd walked in from their vehicle and was less flamboyantly dressed. As they danced, they would throw each other to the side and then pull one another back, leaping up into each other's arms.

To be honest, they were good, although at most ballroom dances in the US we tend to dance with the opposite sex. One couple walked out, but no one else was shocked. At the climax of the dance, the other actor dipped Sacha's head back and kissed him on the lips for about 15 seconds. Little shocks me. I lived all over the States for eight years working as a consulting engineer and was based in San Francisco for two years in the 1960s. Folks from Alabama aren't easily offended and, contrary to what you might think, are inclined to live and let live. But one thing really gets to them – knowing they've been duped.

This is when it hit the fan. The crowd erupted, five or so people screaming at the top of their lungs: "Get out of here. Leave the building." The second actor started lecturing us, barely making himself heard in the chaos. "Our love is wonderful. Ours is true love and you should not feel the way you do." All of course, rehearsed to try to push us further. At that point, I walked over to him and said: "You need to leave." The man ignored me and continued to lecture me close to my face. I wasn't mad but I was irritated. I shoved him hard. Another dancer turned off the lights to stop the filming and someone called the police. When a patrolman arrived, he told the crew: "I don't want to see your faces in Vestavia Hills again."

At some point, the crew realised that things could get out of hand. Maybe they weren't sure what this crazy bunch of old folks were going to do. The last I saw of them was the tail of their long trailer leaving in a hurry.

It wasn't until the following weekend that I grasped what had happened. A Birmingham woman television reporter (a real one this time) called and asked: "You don't think it was Sacha Baron Cohen, do you?"

I'd seen the Borat movie so I knew something about Sacha, a lanky 6ft 3in Englishman. This man didn't have a moustache and black hair, and didn't look that tall from 20 feet away. "Oh, he was that tall," said Brenda. "I saw him standing by the drinks machine."

It had all been a carefully planned operation – aimed at making us look dumb. And those sheets of paper we signed were release forms, giving our consent to the footage being used in Sacha's forthcoming film about Brüno, the gay Austrian television reporter. We were, it turned out, extras working for a pittance.

Calling friends in other ballroom groups the next morning, I found he'd booked to film more dances – in Huntsville, and also Chattanooga and Nashville in Tennessee. Sacha's organised, but we're very organised, too. We put out the word on the internet and they were all cancelled. He was on our territory, so we could do what we liked. Sorry for messing up your schedule, Brüno.

It turns out we were lucky to get off lightly. The Alabama National Guard didn't fare so well. A few days after our dance, Sacha, as Brüno, had fooled them into giving him a uniform, only to strip down to a stars and stripes thong for the cameras.

The way he works is certainly like a military operation. He's highly intelligent, but as he gets more and more famous, it's harder to pull off these sorts of stunts. I don't imagine anyone in Britain would fall for it.

Perhaps he thought we're a bit slower down here and a bit more old-fashioned. I guess he was hoping we'd be outraged by a gay kiss.

I'm afraid I've got news for you, Sacha. Times have changed. Some of us have televisions and occasionally even go to see movies, including your Borat film – which, if you're interested, I thought was good for the first 15 minutes but went downhill after that.

My first reaction was anger. In the South we are taught to trust people, to show hospitality. In return we were insulted. Baron Cohen, I concluded, was little more than an empty shell. Religion has been reported to be important to him, but his personal religion seems to be based on greed and deriving pleasure from shocking others, often being cruel and uncaring – to get what he is after.

The funny thing, though, is that, as time has passed, I've come to admire his skill. It was actually a neat, highly entertaining evening. He had a job to do and he couldn't tell us in advance. So good luck, Sacha, but just one thing. We don't need any more Austrian ballroom tutelage in Alabama, thanks very much.