Protestors on Tuesday covered an official portrait of King Charles III with the face of the eccentric, cheese-loving animation character Wallace to campaign for better animal welfare on farms.
In a video shared by Animal Rising, two campaigners are seen sticking an image of Wallace on top of Charles's face and a speech bubble at a London gallery.
Activists said the protest was aimed at raising awareness about practices at Royal Society for the Prevention of Cruelty to Animals (RSPCA) certified farms.
Jonathan Yeo's striking red portrait of Charles is on display at the Philip Mould Gallery in London, after being unveiled by the king himself last month.
The speech bubble pasted on Charles, who is an RSPCA patron, read: "No cheese, Gromit. Look at all this cruelty on RSPCA farms!" in a reference to Wallace's faithful canine companion.
Animal Rising said the action was aimed at bringing attention to the group's "damning investigation" into 45 RSPCA assured farms, referring to those establishments covered by the body's scheme for maintaining animal welfare standards.
"The lighthearted act played on the king's love of Wallace and Gromit and his status as Royal Patron" of the RSPCA, the group said in a post on X.
"With King Charles being such a big fan of Wallace and Gromit, we couldn't think of a better way to draw his attention to the horrific scenes on RSPCA Assured farms,", said Daniel Juniper, who was involved in the stunt, according to the post.
The owner of the gallery, Philip Mould, said the painting was "safely secured in its frame with protective layers" and that the sticker was only up for "10 or 15 seconds" before being removed by gallery staff.
A police report had been filed, he added.
The RSPCA said it was "shocked by this vandalism" and added that concerns about farms certified by RSPCA Assured were taken seriously.
Charles became a patron of RSPCA in May this year and has previously advocated against animal cruelty, including by banning foie gras in royal residences.