It's (more or less) true, Dai. Turing was using the cyanide powder in some chemical stuff he was working on, and the apple got coated in it, then he ate the apple. His mother never believed he did it deliberately, but then she never new he was gay till he got arrested for it. He'd been depressed over the way his life was going for a long time, and it looked like he might be chucked out of his university job and lose his career because of the court case; also he was being watched by the security services as a potential blackmail-by-the Russians risk, because he knew a lot of secret stuff from Betchley Park. The coroner decided it was suicide.