A hard day in the classroom can usually be eased by something as simple as a mug of coffee. But what if the mere action of drinking it is a stressful event in itself? To watch Chris Sivewright, you might be forgiven for thinking it is. He picks up his mug. Before it reaches his mouth, his hand starts to shake and the mug judders away from his lips. He lifts up his other arm, waves it up and down, the shaking subsides and he finally manages takes a sip. “It’s all about distraction,” he explains. “It’s as if my brain has to concentrate on my hand movement and then ‘forgets’ to tell my neck to swivel.”

Mr Sivewright, 49, suffers from dystonia, a neurological movement disorder characterised by involuntary muscle spasms. The condition affects specific areas, such as the eyes, the neck and facial muscles, causing abnormal movements, and can be extremely painful. For more than 15 years, the business studies and economics teacher has attempted to mask the symptoms associated with his particular type of dystonia - spasmodic torticolis - which affects his head and neck.

“If you didn’t know, you probably wouldn’t notice there was anything wrong with me,” he says. When he shows me into the living room of his Oxford home, he sits down first and directs me to a chair on his left, which, he explains, is because this is the most comfortable position for him to talk.

“I can spot the weak points of a room in seconds,” he explains. “I work out where I can sit and stand without drawing attention to myself.”

In a cafe or restaurant, that means seeking out high-backed chairs, preferably with his back to a wall or window, to make tremors less visible.

If he is with a group of people, he will try to ensure everyone sits to his left so he doesn’t have to move his head too far to talk and listen.

He first suspected all was not well in 1986, when his neck started to jerk every time he lifted his hand towards his mouth. Initially doctors blamed stress. “Dystonia is notoriously difficult to diagnose,” he says. “So I did the usual round of doctors until, eventually, I saw a neurologist. As soon as I walked into the room, he said, ‘You’ve got dystonia and there’s no known cure’.”

Although the prognosis was poor - physiotherapy, painkillers, Botox injections, diet, meditation and magnetic therapy have had little effect - it was a relief for Mr Sivewright to at least know that his affliction had a name.

The timing couldn’t have been worse. He had recently retrained as a teacher after taking redundancy from his job as a buyer for British Leyland. But the physical demands of the classroom - he was a teacher at the Royal Latin school, a secondary in Buckinghamshire - soon proved a challenge. “Writing on a blackboard was difficult, as was writing reports, or marking,” he says. “My head twists one way and unless the paper is fixed I have to hold it, which means I can’t support my head. And standing motionless, listening to pupils, was virtually impossible, so I had to move around a lot.”

Although he developed a range of coping techniques, his condition couldn’t escape keen-eyed students. “I’d just tell them I’d drunk too much coffee,” he says. “But as things got worse, it became too difficult to hide. One of my coping strategies was to set lots of student-led work. I’d give them topics to prepare, which they’d present in lessons. I’d listen and contribute, which meant I could keep moving around but, as with any teaching strategy, there’s only so much students can take before they get bored and stop concentrating.”

It would have been easy to have given up, but Mr Sivewright’s entrepreneurial streak won through. He had already established the Oxford School of Learning - a private college that specialises in one-to-one tuition, primarily in business studies and economics. The expansion of the college services to include online tuition, online resources for teachers and A-level business studies revision conferences means he can stay in a profession he enjoys, and manage his condition. Lessons for his online A-level business studies course are delivered via a weekly email and a follow-up discussion on his online forum. Many of his students sign up to support teaching at their school or college. Others rely solely on his online materials.

But even within the relative “safety” of virtual or one-to-one teaching, managing his condition is still a priority. He always sits to the left of his students - he doesn’t tell them about his condition - and uses a swivel chair, so he doesn’t have to remain motionless. Lessons are discussion-based, with students researching and presenting topics to him, and he rarely writes anything down for them. “It’s a case of having to adapt rather than wanting to,” he says. “Teaching was my life, and that hasn’t changed. It’s just the method of delivery that’s different.”

Chris Sivewright is currently running an essay competition on dystonia for teachers and students. The prize is pound;100. For details, visit: www.dystonia-support4u.co.uk schoolscomp.php.Oxford School of Learning: www.osl-ltd.co.uk. The Dystonia Society: www.dystonia.org.uk0