I knew that this was an infamous case of antisemitism, but never knew any of the details, until In our Time (Radio4).

Dreyfuss was from Alsace, and like others from that contested area, determinedly patriotic. He was one of a new generation of middle class citizens who rose through the ranks of the military on the basis of merit. He was charged with treason on the basis of a letter found in a wastepaper basket; this was subsequently shown to be a forgery but the sentence was not repealed on the basis of further evidence that the military considered too politically sensitive for disclosure.

He was court martialled in a public display that included his ceremonial sword being broken. He was then sentenced to solitary confinement on Devil's Island. He endured more than a year of the psychological torture of social deprivation, he had no view of the outside world except for the sky above his compound, and his rations were insufficient to prevent malnutrition.

The military closed ranks against all attempts to prove his innocence. The officer charged with forging the original letter became a popular figure, his family supported by public donations. Eventually Emile Zola wrote a public letter condemning the authorities for their handling of the case.

Dreyfuss was eventually released after being offered clemency. His family thought this was the only way to prevent his death on Devil's island. His supporters were disappointed that his innocence was never officially accepted or his maltreatment compensated for.