LONDON (AP) — London arts center the Barbican has cancelled a show called “Exhibit B” amid protests over it featuring black artists in chains and in cages.

Protesters demonstrated outside The Vaults, the show venue, and police were called. The Barbican charged that despite their offer of dialogue, the protests were “not done in a peaceful way.”

The arts center defended the work, arguing that it raised issues about racism “in a serious and responsible manner.”

“We believe this piece should be shown in London and are disturbed at the potential implications this silencing of artists and performers has for freedom of expression,” the Barbican said in a statement.

Some 20,000 people signed a petition to protest the show, calling it “an outrageous act of complicit racism.”

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