Activist group BP or Not BP? has placed a giant 'Trojan Horse' scultpure inside the courtyard of the British Museum.
The action, which signifies an escalation in the group's campaign against oil company BP's sponsorship of the museum, precedes a 1000-person protest planned for Saturday.
Group member Helen Glynn said the horse is "the perfect metaphor for BP sponsorship".
"On its surface the sponsorship looks like a generous gift, but inside lurks death and destruction."
Though the group snuck the sculpture inside early Friday morning, it has requested the museum leave it there overnight: "We do not want to block any entrances or cause any disruption to the flow of people coming in or out of the museum.
"We acknowledge that this is an unusual request, but as your chairman has said, climate change is 'the great issue of our time'. Business as usual must change."