A long time ago, I was transformed from resolute geek into a salesman. I’d written an application, commissioned by an international software publisher that subsequently disappeared in a spectacular way. It was an MSDOS program for managing serial communications for people who didn’t like computers much, but had to use them. It was good.

Suddenly, shoehorned into a shiny suit, polished shoes and new briefcase I was forced to trudge around the software industry selling this application that had taken me six hard months to write. Technical people make bad salesmen. They tell the truth at inopportune moments and thereby unsettle their audience. They tend to be short on charm. I was as bad as anyone, but I had no choice.

It was during this awful time in my life that I had my worst-ever sales presentation. I remember it well: in fact, when I get insomnia, it is re-enacted in my minds eye as though on some synaptic DVD player.

It all started pretty well. I turned up at a smart office in West London and was greeted effusively by all the right senior staff that all declared them interested in adopting the product as their own. It fitted well into their product line. In the boardroom, I ran through the features of the program to general grunts and nods of genuine interest. I’d got the patter off pretty well by then.

I then started the demonstration of the product. For some strange reason to do with the configuration of the machine to be used for the demonstration, the application did not work properly (this was before laptops). I reached for the briefcase to get out a device for checking the serial interface and started to rummage.

At that point, a pistol dropped out of the briefcase.

The pistol was, of course, a fake. Unknown to me, my son, then aged three had put the cap-gun in my briefcase. He had only just been allowed a toy gun, and to reward his patience, I’d bought him a really nice one that looked pretty real. No plastic for my boy. Perhaps he felt that I looked nervous that morning so he slipped the gun in the briefcase as an act of reassurance.

If I have any advice to give to salesmen, it is that, if a pistol drops out of ones briefcase during a presentation, do not hurriedly stuff it back in hoping that nobody has noticed.

I made that elementary mistake, stuffing the pistol back in the briefcase. Ridiculous, I know. I should have laughed and explained. Instead, I went beetroot red and stammered. The audience looked strained and nervous, but became more and more noisily appreciative of the product I was trying to sell them. I suspect that they just heard the thump as the gun hit the table and caught a glimpse of cold steel, and the magnum calibre. It did not help the rapport that, by this time, my eyes were bulging with panic. At the end of the presentation they clapped, but their eyes told a different story. They promised all sorts of deals but I could tell something was wrong. They escorted me to the door, and I walked once more out into the street, gripping my briefcase..

Behind me I heard a click as the door was locked on the inside and I caught the glimpse of people running down the corridor. Oh dear, I thought, that presentation did not go so well.