Claustrophobia sufferer Henrietta Roussoulis tries out a new therapeutic technique

Cast an eye over the person sitting next to you. Go on, have a good look. They might look calm, capable and confident, but the chances are that underneath that cool exterior lurks a deep-seated irrational fear, be it of needles (aichmophobia), cats (ailurophobia), or even, in the case of one colleague, woolly cardigans (blousophobia?). According to a recent report by the Royal College of Psychiatrists, one in 10 of us suffers from a phobia and numbers are on the up.

Personally, Ronald McDonald has always filled me with a sense of dread, but as bêtes noires go, he's not nearly as debilitating as the prospect of getting stuck in a toilet cubicle. I have been claustrophobic for as long as I can remember, and the curtailments to my life are not limited to the risk of humiliation in public lavatories (which I never lock). I also refuse to get into lifts alone (not funny when you've got a job interview on the 15th floor).

It's an irrational fear that therapist Terry Elston knows about all too well. He has devoted his working life to helping people overcome mental obstacles using an increasingly popular neuro-linguistic programming technique called Time Line Therapy (TLT), which he promises can cure me of my phobia in less than 20 minutes (which is just as well considering a one-hour session will set you back £150). Originally developed, and trademarked, by the American psychotherapist Tad James in 1985, it is a set of techniques based on the principle that our mind is programmed to store "learnt strategies" such as how to drive, which we then use on autopilot. But, according to Elston, as well as these positive strategies, we also store negative ones, creating phobias that are deeply programmed.

It is our "reticular activating system" - a protective mechanism created by the unconscious mind - that tells us when we are afraid of something. This mechanism alerts areas of the brain to think and feel, and Elston says that "whenever the unconscious mind encounters anything that reminds the brain of that particular event, it goes on red alert and tells the body that it is in danger." The aim of TLT is to dissociate the present from the past, so that past memories no longer affect your present behaviour.

This is just one of many explanations of our phobias, and there are as many theories on how best to cure them. Cognitive therapy, a popular approach, involves physically facing up to your phobia and has been used by the likes of Russell Crowe, who overcame his fear of the sea by playing Captain Jack Aubrey in Master and Commander. TLT is different in that it deals with the unconscious mind: the idea is that a series of guided visualisations will help re-programme the unconscious mind and delete the negative strategies. Elston aims to cherry-pick the best of both techniques.

As I arrive at his studio in Brighton, I'm feeling less than optimistic: the idea of a total stranger relieving me of a lifelong phobia in less time than it takes me to eat a Big Mac is inconceivable. As part of the first exercise, which deals with the conscious mind, Elston asks me if there has been any one event that might have triggered my claustrophobia. I recount the time when - aged 20 - I was using a friend's bathroom. I turned the door handle and found it was stuck. I was alone in the basement flat and knew no one would be home for hours. Within seconds I was panicking. I started trying to bang down the door and was screaming in the hope that someone might rescue me.

As it turned out, I wasn't stuck at all: I had been turning the door handle the wrong way and in the midst of my panic, sobbing like a baby, I managed to let myself out. The whole incident lasted minutes - maybe even seconds - but I will never forget the intense feeling of imminent death that came over me in that short time, as I wondered what I had done to deserve such an undignified end.

We work on the cognitive exercises first. Elston takes me through a list of questions: how do I "do" fear? Why am I so good at it? These seem ridiculous, but in replying to them, I am articulating the emotions that I experience, such as intense panic. I'm also visualising the situations in which these emotions arise. With each mental image that I describe, Elston puts a finger on one of my knuckles, as if tapping in to this negative pool of emotions. He then takes me through a list of positive emotions: can I describe an event that made me feel motivated? Again, I feel a gentle tap. When we discuss a situation of fear, Elston makes me verbally and visually replace this negative event with one of the positive experiences I have just recounted.

Now for the Time Line Therapy. This is the part I have been dreading - the route into my unconscious doesn't involve hypnosis but I start to worry when Elston pumps up the volume on the pan pipes that have been tinkering away in the background. My fears get worse as he explains that TLT is based on the idea that phobias can be triggered by events that occurred in a previous life - your unconscious mind stores this memory but your conscious mind isn't aware of it.

Frankly, I'm a bit thrown. Reincarnation is not exactly central to my beliefs in the way it seems to be to Elston's but what the hell, I give it a go. "Point to where your past lies," he instructs. For no reason at all, I stick my hand out to my right. When asked to point to my future, I indicate straight ahead. "Close your eyes and visualise the line," he says. What colour is the line of my past? "Black," I reply. And the colour of my future? "Red." I obediently imagine I am floating above this imaginary line, "visiting" all phobia-related events that I can remember and trying to find ones I can't. I am totally relaxed, but the cynic in me is finding it hard to embrace Elston's theories. However, I do start picturing a recurring dream of mine, during which I am buried up to my neck in sand and can't get out.

It's time to test whether or not the fear has gone. Eyes closed again, I visualise travelling back along the line to my key bathroom incident. Am I still scared? Well, yes. But the next exercise is more successful. Elston asks me to visualise myself sitting in a cinema. On the screen is my key bathroom-moment scene - I am to put myself in the picture and go through it in colour. He then tells me to rewind it and play it through again, this time in black and white. We repeat this process again and again. Each time I replay it I imagine a better version of the story - eventually the story ends with me calmly letting myself out of the bathroom. It's like editing a film so it only contains the bits that you are happy with.

The session is over. Did it work? A couple of hours later, I almost manage to lock a cubicle door but can't quite bring myself to do it. A week later I'm about to go on the London Eye. Not wanting to embarrass myself, I clench my fists and board the glass pod. I feel my heart racing. If claustrophobia is partly to do with not being in control, I rationalise that I'm in a situation where I am in control - I have chosen to be here and I don't actually want to get out. Which suggests to me that although Elston cannot work magic, one more session would probably do the trick.

It has been a useful, although not entirely successful experience. I still worry about the time I devote to analysing the necessity of putting locks on toilet doors. But I am not alone: as a child, John Mortimer was locked in a hotel lavatory in Nice and is seemingly unaffected by the fact that he has not locked the door since.

Sessions cost £150. Terry Elston can be contacted on