Passage: Taylor was badly injured in 1984 when he was run over by a car while crossing Old Compton Street in London. The effect of the accident led to his retirement in 1985. In his last years, he endured Parkinson's disease, which left him incapable of writing. His last public appearance was at his 80th birthday, in 1986, when a group of his former students, including Sir Martin Gilbert, Alan Sked, Norman Davies and Paul Kennedy, organised a public reception in his honour. He had, with considerable difficulty, memorised a short speech, which he delivered in a manner that managed to hide the fact that his memory and mind had been permanently damaged by Parkinson's disease.

Question: What left him unable to continue writing?
Parkinson's disease