An international project featuring a rapist discussing his crime on stage has drawn both condemnation and support. So should a perpetrator be given a platform to share his experience?
"There's a rapist in the building," the protesters shouted as they briefly blocked the entrance. "Get the rapist out."
Their banners and loudspeakers were an unusual sight outside a venue better known for world-class concert performances than controversy.
The anger at London's Royal Festival Hall at the Southbank Centre on Tuesday evening was over South of Forgiveness, an event that would see a woman inviting the man who raped her to discuss the impact of his actions.
The discussion between Thordis Elva, from Iceland, and Australian Tom Stranger had already been dropped from a women's festival at the weekend following pressure from campaigners.
But it was rescheduled after organisers of the Women of the World (WOW) Festival said the debate was too important to silence.
"Rape is one of these critical issues and we need to shift the discourse around it, which too often focuses on rape survivors rather than rape perpetrators", Jude Kelly, artistic director of the Southbank Centre, said in a statement.
Diane Langford, one of the protesters waving placards on the banks of the River Thames, condemned the decision.
"I'm here because I feel a rapist is profiting from his rape," said the 75-year-old, herself a survivor of rape.
"I don't believe there can ever be impunity for a rapist."