The US-based activist group the Guerrilla Girls told The Art Newspaper that they would infiltrate Frieze—and on Thursday they did. Co-founders Frida Kahlo and Käthe Kollwitz (members adopt the names of dead female artists) wore gorilla masks and gave out “just a handful” of stickers protesting against billionaire art collectors before they were stopped by security staff, Kahlo says. One sticker stated: “Art is sooo expensive! Even for billionaires! We completely understand why you can’t pay all your employees a living wage!” Security staff are trained to enforce a strict no-leafleting policy across the fairs, a spokesman for Frieze says, adding that the group was welcome and that members stayed to attend Coco Fusco’s lecture performance as Dr Zira, the chimpanzee scientist from Planet of the Apes. “We did not realise [Frieze] was not a zone of free expression,” Kahlo says. The Guerrilla Girls are in residence at Tate Modern’s new Tate Exchange space until Sunday 9 October.