I am a high-functioning autistic, yes, but definitely autistic. This means I can't be entirely certain that everything you are about to read is right. Autistics tend to get things wrong, to misread situations. I have always known I was to some extent dysfunctional, but I used to revel in being an eccentric. At school I gained both a "first in form" and a progress prize, but my academic life thereafter was a failure. I lasted a year at drama school, where I was unable to relate to others, or to realise the promise that had put me there. At the Polytechnic of North London, where I studied philosophy and computer science, I was labelled "mad Paul".

In May last year I went to the cinema in Bristol with an old friend, who has Tourette's. He, his wife and baby were moving house, and I thought a noisy action film - it was Van Helsing - would give him the distraction he needed. The cinema was full, but four children were running around the auditorium, punching each other and being disruptive. An hour and a half into the film, my friend asked them to be quiet. I was so worried they'd turn on him, I jumped out of my seat and put a firm hand on one of them, on the shoulder; I wanted to distract them.

We all froze, and the children ran out of the cinema. When we left, we were met in the foyer by two police officers, who took us to the police station and charged us with common assault. I remember the room was very hot, but I felt very cold. I made a statement, and seven long months later we were acquitted of any wrongdoing - of 260 people in the cinema, none had witnessed an assault; there was no further evidence.

My brother Martin and his partner, Alicia, however, were adamant that I be tested for autism, so I visited the Autism Research Centre, Cambridge, where I was found to be on the "autistic spectrum of disorders". Getting the diagnosis was a relief, like coming out: no more bluffing the world or kidding myself I would "get better". It turned out that my inability to handle ordinary social encounters was normal. The best way of explaining this is that it feels as if parts of me have been deleted. I can be insensitive; I am often not sure when to speak. Autistics are in that sense buried alive, getting little sense of emotion from others, talking either incessantly or not at all.

I have mastered the art of being a simulacrum, a fake "neurotypical". I can appear to be listening when my mind is racing with boredom. I might seem to hesitate before answering, but I will have had my reply ready for some time.

People think I relate well socially. I can be funny, and I have held down jobs, had relationships, maintained long-term friendships. For three years I had a job selling West End theatre tickets, and I loved those three-minute relationships formed with people at the other end of the phone. But my memory has a life of its own, which means I've always underachieved and failed to pick up professional qualifications.

Autistics often have one thing they do particularly well. In my case, it's improvisation: I can write and I can act, but I have never had the social skills for a career in the theatre. I've noticed many autistics are into science fiction and computers, which figures: one of them is all about alienation, the other is all endless streams of information. We don't get the more subtle, sensual undercurrents of life. Autism can be very lonely; we are unable to relate to people in an intimate way.

I now teach a meditation class for the autistic. I wanted to create a safe space where people can sit and not speak for a while - something many autistics think they can't do.

Autism is officially a disability, but I am ambivalent about describing myself as "disabled": it often changes people's (and employers') perceptions in a way that's not helpful. Easier not to acknowledge a job application from an autistic than to interview and then turn them down. I think people can identify too strongly with their disability: they hide behind it and think life is treating them unfairly, when push and shove is the rule for all of us, autistic or otherwise.

In some ways I think that, if you know you're autistic but everything else in your life is in place - job, family, friends - you're better off keeping your head down and not getting a diagnosis. But if you do, it's nothing to fear: we are sane, we are accountable, we are lovable.