Climate activists from Just Stop Oil have painted over the grave of British naturalist Charles Darwin at London's Westminster Abbey.
Two members entered the church and used spray chalk on the white marble gravestone, the campaign group said in a statement.
The activists wrote "1.5 is dead" in orange - a reference to confirmation that last year was the first to breach the key global warming threshold of 1.5C.
"We have passed the 1.5 degree threshold that was supposed to keep us safe," the activists said.
"Millions are being displaced, California is on fire and we have lost three quarters of all wildlife since the 1970s.
"Darwin would be turning in his grave to know we are in the midst of the sixth mass extinction.
"World leaders must stop burning oil, gas and coal by 2030."
Charles Darwin, best known for his theory of evolution by natural selection, died in 1882.
He is buried in Westminster Abbey's Scientists' Corner, where Isaac Newton and Stephen Hawking are also interred.
The church confirmed the incident in a statement.
"The Abbey's conservators are taking immediate action to clean the memorial and do not anticipate that there will be any permanent damage," a spokesperson said.
"The police were called to the scene and dealt with the incident. The Abbey remains open for visiting and worshipping."
London's Metropolitan Police said that two women had been arrested on suspicion of causing criminal damage at Westminster Abbey.
They have been named by Just Stop Oil as Alyson Lee, 66, a retired teaching assistant, and Di Bligh, a 77-year-old former chief executive of Reading Council.
Activists have staged a number of high-profile protests in Britain including by disrupting sports and theatre events, painting over the US Embassy building in London and throwing soup at Van Gogh paintings.
Westminster Abbey is the venue for royal weddings, coronations and burials and a major tourist attraction.
Additional reporting PA
