Activists have taken a Trojan Horse inside the gates of the British Museum to protest at BP sponsorship.
The object is 13ft (4m) tall and can seat 10 people inside, pressure group BP Or Not BP? said.
The British Museum said it was “awaiting advice from the police”.
Protesters want to stay in place, on the outside forecourt, overnight, ahead of a mass protest planned for Saturday.
The stunt is timed to coincide with the museum’s BP-sponsored Troy exhibition – the wooden horse is a famous part of Greek legend.
A British Museum spokeswoman told the PA news agency: “We can confirm a small group of 15 protesters are trespassing on site.
“We are awaiting advice from the police. We regret that this action may mean disruption to visitor access to the galleries this morning.”
Critics say the oil giant’s sponsorship of institutions like the British Museum acts to “artwash” BP.
The Royal Shakespeare Company and National Galleries Scotland has severed ties with the company, while the National Theatre cut links with Shell.
Activists say the horse, featuring the BP logo, was “snuck into the museum’s courtyard at 7.30 this morning” through a side gate.
A letter handed to the museum requests that it be allowed to stay in place until Saturday.
Helen Glynn, from BP Or Not BP?, said: “The Troy exhibition has inspired us to create this magnificent beast, because the Trojan Horse is the perfect metaphor for BP sponsorship.
“On its surface the sponsorship looks like a generous gift, but inside lurks death and destruction.
“This is our 40th performance intervention at the British Museum. For eight years our peaceful creative protests have been dismissed and the museum has continued to back BP.
“Now the planet is literally burning.”