Long before the 20th century, and its still going on.
The site of Clifford's Tower, the keep of York's medieval castle, still bears witness to the most horrifying event in the history of English Jewry. On the night of 16 March 1190, the feast of Shabbat ha-Gadol, the small Jewish community of York was gathered together for protection inside the tower. Rather than perish at the hands of the violent mob that awaited them outside, many of the Jews took their own lives; others died in the flames they had lit, and those who finally surrendered were massacred and murdered.
Understandably, this appalling event has become the most notorious example of antisemitism in medieval England. Yet, it was by no means an isolated incident, but rather the culmination of a tide of violent feeling which swept the country in the early part of 1190.