John Bolton, the former US ambassador to the United Nations, faces a citizen's arrest when he addresses an audience at the Hay Festival in Wales this evening.
George Monbiot, the journalist and activist, is planning the action because he believes Mr Bolton is a "war criminal".
He said he was surprised that Mr Bolton would be allowed to "swim through the politest of polite soirees – which is of course Hay."
Mr Bolton, who was the American ambassador to the UN from August 2005 to January 2006, is due to talk at the Hay-on-Wye literary festival at 6.30pm on international relations.
I'd rather see the actual authorities from the Hague arrest him, but so much for wishes and good intentions.