Even after 3,000 hours of French tuition, I can't order the right amount of cheese

After roughly 3,000 hours of intense tuition in such diverse pedagogic settings as a secondary school in Liverpool, evening classes at the City Lit and conversational practice with Martine in the privacy of my own home, I am now more or less able to make myself understood at the cheese counter of an average French supermarket.

I haven't reached the advanced stage where I can ask the names or the distinctive qualities of all the cheeses in front of me, but I can say "Emmental", "Roquefort" and "Brie" with sufficient assurance to suggest that these are my cheeses of choice, rather than the only ones that my vocabulary will support.

There was one occasion in Montpellier last year when I had become so intoxicated by three previous purchases of Emmental, Roquefort and Brie that I threw caution to the wind and declared an initial interest in Reblochon. But there must have been a hint of hesitance in my voice, because the assistant not only failed to move towards anything resembling a soft, creamy cow's cheese, but instead adopted that infuriating French custom of responding to a simple request with a sentence of such length and elaboration that I had no alternative but to shake my head vigorously and revert to my trusted formula. "Roquefort," I said, with as much firmness as I could muster.

This brings us to the tricky question of amount. For some time now, I have favoured a simple "deux cent grammes". Although this is rather more than I intend to consume, it steers me well clear of the numerical complexities of 150. Nor is this the limit of my quantitative vocabulary. When it comes to jambon or tarte aux pommes or gigot d'agneau, I can switch with relative ease to "deux tranches". It was precisely my overconfidence in this respect that led to a minor disaster at the Casino supermarket outside St Remy-de-Provence last week.

As usual, I had forcefully demanded "Emmental", and the assistant, to my satisfaction, had immediately selected a large block of exactly the right cheese. "Deux cent grammes" was on the tip of my tongue, but something about the way her knife hovered gave me the licence I needed. "Deux tranches," I announced, confidently. It was a fatal error. Even as her knife began to cut, I realised that a single tranche from the block would be more than sufficient to replace several of the large tiles missing from the base of our villa's swimming pool. As the first tranche collapsed like a condemned tenement block on to the greaseproof paper, I searched for a phrase that might halt her before she began on the second tranche. "Seulement un," I protested, pointing to the existing tranche. "Seulement un."

Back at the villa, several people tried to explain how this simple phrase could have been so misunderstood. Not only had the assistant completed the second tranche, but she had proceeded to slice a third tranche, and then pushed the entire package over to me with what sounded suspiciously like an ironic "C'est tout?". Within minutes, I was at the checkout counter, handing over F300 for what had been intended as the grated accompaniment to a medium-sized jar of fish soup.

Over dinner, Geoff was the only member of the villa party who tried to find some words of consolation. "Look on the bright side," he said, gazing round the pyramid of grated Emmental that dominated the table. "Think what it would have been like if you had chosen a cheese that wasn't already plein de trous." Now that I have had time to look up "trous", I can see that it was rather a good joke.