The three-line format works as well for the modern activist as it did for the Italian poet Dante Alighieri in the 14th century.

71 dead
And still no arrests?
How come?

Three billboards bearing these words, in reference to the people who lost their lives in the Grenfell Tower fire, were attached to lorries and driven around London, including past the Houses of Parliament, before being parked outside the Grenfell complex.

The protest was inspired by the award-winning film Three Billboards Outside Ebbing, Missouri, which centres on Mildred Hayes, who rents three abandoned billboards to draw attention to the unsolved murder of her teenage daughter. The red and black signs – “Raped while dying”, “And still no arrests?”, “How come, Chief Willoughby?” – become symbols of a grieving mother’s fight for justice against all odds: the police chief, the fictional Midwestern town she lives in and the loss that continues to haunt her.

Since the film’s release, visual homages have popped up around the world calling attention to a wide range of issues. In January, a Twitter user posted a picture from the Women’s March in New York City of three signs that called for the impeachment of Donald Trump. The following month, the British advertising agency BBH Labs used the same concept for a campaign for the bereaved families, survivors and evacuated residents of Grenfell Tower and the local community.

More examples followed. An activist parked three trucks carrying billboards outside a Florida senator’s office, days after 17 people were killed in a mass shooting at Marjory Stoneman Douglas high school. “Slaughtered in school”, “And still no gun control”, “How come, Marco Rubio?”, they said. Outside the UN headquarters, three billboards urged the security council to vote for a ceasefire in Syria. In Kosovo, an arts collective put up three billboards outside the police headquarters asking questions about domestic violence.

Many of the billboard campaigns are attacks on those in power for failing to keep people safe and hold guilty parties to account. After the Grenfell blaze in June last year, the authorities opened a public inquiry. But no arrests have been made, and survivors and families of the victims have complained that their voices are not being heard.

Yvette Williams from the Justice4Grenfell campaign told the Guardian: “Eight months on from the Grenfell tragedy, we felt that the disaster was fading out of the public consciousness. Key questions were being ignored, little action had been taken, and our community still remained traumatised and grieving.

“This was the catalyst for the three billboards outside Grenfell. The film’s message of a mother’s quest for justice and the powerful message of ‘the more you keep a case in the public eye, the better chance you have of getting it solved’ resonated with what was happening in North Kensington.”

Williams, a former primary school teacher and a policy adviser on equality and diversity for the Crown Prosecution Service, said the billboards were not only a creative way for the community’s voice to be heard, but an effective medium for a younger generation who often use the visual and cultural references of film to make sense of the world. “It would be instantly accessible to a wide audience who don’t use the mainstream media, but other references,” she said.

Experts say there are psychological reasons behind the power of the billboards. Dr Mario Campana, a lecturer in marketing and consumer behaviour at Goldsmiths University, said: “Imagine having the same billboards in the middle of Piccadilly Circus; they would not have the same impact, because there are many more stimuli which the consumers are exposed to, such as animated boards and lights.

“In these conditions, consumers go through sensory overload and start filtering information.

“And when it comes to colour, red and black are quite powerful. Psychological research has shown that red is usually associated with a state of activation. With passion or love, as well as with warning and danger. Black is usually associated with negative feelings or mourning.”

Campana said the billboards generate strong reactions because they provide “a controversial message within a closely knitted local community”, where people have rituals, traditions and a sense of moral responsibility towards each other.

“Advertising is culturally situated and its impact depends on the consumer culture behind the message,” he said.

Activists believe the power of advertising can be harnessed to remind people how little has been done to deliver justice to oppressed and bereaved people.

After winning the Oscar for best actress for her role as Hayes, Frances McDormand said “billboards still work, so I think that it’s really exciting” and praised “the idea that activists are taking that kind of statement and putting it out there”.

Williams said Justice4Grenfell was grateful to McDormand for her backing, which “enables support for protests to reach an international audience rapidly”.