Many executives do not realise that a large part of their job often involves some form of speaking before an audience. It usually hits them just when they least expect, perhaps at a meeting, when they may be asked to explain their agenda, at short notice, to a group of people they don't know.

They need to learn that the art of speaking with conviction is not especially different, whether one is addressing five people or five hundred.

It is commonly agreed that the prospect of public speaking generates a degree of anxiety that is completely out of all proportion to the actual penalties of making a poor speech. Psychologists claim that this is based on a fear of fear, and it sets up stress-levels that are liable to increase as the speech continues.

How can we deal with this autonomic stress response that takes over our body (and mind) when having to face an audience?

First, there is the classic debate over whether it will help your confidence to rehearse your presentation word for word. Some say this will sound too much like a recital, and not a sincere message. Yet professional actors have to convey sincere emotions while speaking well-rehearsed lines. And public speaking is a branch of acting. So the answer is that sufficient rehearsal will give you the added confidence of knowing that you won't suddenly dry up. But... you don't have to stick precisely to the lines. This gives you the flexibility to adapt your speech to local conditions. For instance, you may need to respond to an interruption or other audience reaction. Be rehearsed, but be free to think on your feet. A recommendation from the actor's rule-book, that will help your body's response, is the physical matter of breathing. Nothing looks or sounds more amateur than a presenter suddenly gasping for breath because they've failed to study simple breathing techniques. Regular natural breathing, as though you're just addressing a couple of friends, will induce normal spontaneous speech, and maintain a relaxed atmosphere that will encourage rapport and empathy with your audience.

Finally, I knew one lady who used to suffer a serious fear of public speaking, until her therapist gave her this tip. Just before going on stage, think back to one particular moment when you were truly happy and confident, and imagine yourself being there - in fact, just like an actor in a role. Simply, be that confident self as you walk on. And that is how an audience of people you do not know, will view you and respond to you at the crucial first moment.

Successful speaking before an audience is essentially about self-confidence and self-image. The key factor in this is realising that knowing your subject (backwards) is not an option. And you must be confident that you are able to answer (or deflect) virtually any question from the audience, with apparent ease. Good luck!

The writer is a BBC broadcaster and motivational speaker, with 20 years' experience as CEO of Carole Spiers Group, an international stress consultancy based in London.