Four people have been arrested after smearing chocolate cake over a wax statue of King Charles III at Madame Tussauds in London on Monday (local time).
The protesters were part of the climate group, Just Stop Oil, and were calling for the Government to halt "all new oil and gas licences and consents".
In a video posted to the group's Twitter two protesters can be seen removing black shirts to reveal white tops with "Just Stop Oil" written on them.
One protester then grabs a cake and smashes it into the monarch's face before the other does the same.
They can be heard yelling "this is time for action".
London's Metropolitan Police said four people were arrested for criminal damage on Monday.
"We responded quickly to an incident at Madame Tussauds after two people threw food at a statue at approximately 10:50hrs. Four people have been arrested for criminal damage related to this incident," police said in a tweet.
Madame Tussauds said the wax statue is temporarily closed while it works with police.
"Our security team dealt with the incident quickly and we are working closely with the Metropolitan Police on this matter. The attraction remains open, with our Royal Family set closed temporarily."
It follows similar action on Monday when two activists pelted Claude Monet's Haystacks painting with mashed potatoes at the Barberini Museum in Germany.
The activists were from the anti-fossil fuel group Last Generation.
And it follows another protest by Just Stop Oil earlier in the month where members of the group threw tomato soup on a Van Gogh painting in the National Gallery in London.
Footage shows two people wearing Just Stop Oil T-shirts opening cans of Heinz tomato soup and spattering it on van Gogh's Sunflowers (1888) before glueing themselves to the wall. The protesters were arrested for criminal damage and aggravated trespass.
The protesters - Anna Holland, 20, and Phoebe Plummer, 21, - pleaded not guilty at Westminster Magistrates' court earlier in the month to the vandalism of the NZ$148 million painting.
They appeared in the dock together only speaking briefly to confirm their name, date of birth, addresses and to enter their pleas of not guilty to criminal damage to the value of less than £5,000 (NZ$10,000).
They were released on bail by District judge Tan Irkam under the conditions they do not enter galleries or museums and do not have paint or adhesive substances in a public place.
The judge set their trial for December 13 at the City of London Magistrates' Court.
London's National Gallery confirmed the painting is now back on display.
