Sue Gilpin reached the end of her 20-minute lecture to an audience of eminent neurologists and sat down. It had gone well. She had not lost her place in her notes; she had not stumbled over long words; she had not allowed her right arm to hang limply or her right foot to drag. There was considerable applause.

Fifteen years ago, such considerations would never have occurred to her. She was on her feet, fluent and witty, in front of an audience all day - as a senior manager, head of English and a GCSE chief examiner at Sir Harry Smith community college, an 11-16 secondary in Cambridgeshire. She suffered a massive stroke while on a school trip to Germany. It paralysed her right side and robbed her of spoken and written language: “I could say four words: ‘yes’ and ‘no’ - which I got the wrong way round - and ‘oh dear’. I still reverse words.”

From that apparently dire state, Ms Gilpin, 57, has built a new life, centred, extraordinarily, on public speaking. Today, she travels around the country and the world explaining to doctors, speech therapists, stroke victims’ families and Women’s Institute groups what it feels like to develop aphasia: the condition in which the brain’s language areas cease to work properly, impairing speech, writing, reading, gesture and understanding. She lost all these faculties, apart from understanding.

Fifteen months after her stroke, realising she could never go back to teaching, she enrolled on an MA course at Cambridge University’s Institute of Education. Despite intensive speech therapy, she was far from ready. “When you have taught language you can’t believe yours has gone. I couldn’t spell, I couldn’t write, I couldn’t count. I went to the first seminar and I understood what the lecturer was saying, and I tried to write notes, but I couldn’t because I couldn’t identify the first letter of each word.

“Eventually, I took in a tape recorder and transcribed the tape before the next session. It took hours and hours. My friends did my homework because I couldn’t. I wrote the MA in simple sentences, but I knew I was improving all the time. It took me four years, but I got it.”

During that time she also helped form a Cambridgeshire branch of Speakability, the national charity for people with aphasia. As her therapy continued and her speech returned - today she reckons she has 75 per cent of it back - she was invited to become a national Speakability trustee, and then, in 1992, to speak at its London conference on education after a stroke. She was not sure whether to accept. Speaking without notes, she invariably repeats herself. Writing is a struggle. Nevertheless, with help from a dyslexia teacher friend, she wrote and delivered the speech. Then Speakability asked her to go to the Brussels meeting of the International Association of Aphasia (IAA) and give it again. It was, Ms Gilpin says, the first moment since her stroke when she thought: “I am going to be useful.”

Since then, she has become president of the IAA, as well as helping to form a new charity, the Communication Disability Network (known as Connect). The British Council recently sponsored her on a lecture tour for health professionals in Argentina. It was the first time they had heard how aphasia feels from the inside: “It’s quite unusual for an aphasic person to get up and speak. Aphasia is still a hidden condition because people don’t understand what it is. You don’t change your personality or your intellect, but they’re locked in your brain.”

Her presidency runs for another year, after which she will move on, she says. She plans to study astronomy and archaeology with the University of the Third Age: “I’ve done this for 10 years; I don’t want to be viewed as an aphasic person any more.”

She is no longer the person she was immediately after her stroke - “I was so frustrated and angry” - but she will also never be the person she was before.

“I loved to use long words and I can’t do that any more. I was witty, and now my wit is silent. But I am bolder. I’m more blunt. I don’t have the language to blanket my speech. That means I’m not tactful, but it saves time. If you want to do something, say it. Don’t hint it. Because it’s a much quicker conversation.”

Speakability is a charity which supports people with aphasia: www.speakability.org.uk. Connect is a new charity providing research, education and therapy to enable people with communication disorders to find new ways of ‘talking’: www.ukconnect.org.