Animal rights activists have pasted a picture of the stop-motion cartoon character Wallace, from Wallace and Gromit, over the new portrait of King Charles, in a protest highlighting alleged cruelty at RSPCA-accredited farms. Two supporters of the group Animal Rising entered the Philip Mould gallery in central London after midday on Tuesday and carried out what they described as a “comedic redecoration” of the portrait with apparently self-adhesive posters pressed into place with paint rollers. In a video posted by Animal Rising on Instagram, the king’s face was covered with the image of Wallace, while a second poster, in the shape of a speech bubble, said: “No cheese, Gromit. Look at all this cruelty on RSPCA farms!” The king is the royal patron of the RSPCA, which runs an accreditation scheme of farms under the label “RSPCA assured”. Over the weekend, Animal Rising published an investigation into 45 such farms, in which it alleged animal cruelty and suffering at every one. The group alleged 280 legal breaches across the farms. “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, a former nursery teacher named by Animal Rising as one of the pair who carried out the action. “Even though we hope this is amusing to his majesty, we also call on him to seriously reconsider if he wants to be associated with the awful suffering across farms being endorsed by the RSPCA.” The gallery said no damage had been done to the portrait. An RSPCA spokesperson said: “We welcome scrutiny of our work, but we cannot condone illegal activity of any kind. We remain confident that our RSPCA assured scheme is the best way to help farmed animals right now, while campaigning to change their lives in the future. However, any concerns about welfare on RSPCA assured-certified farms are taken extremely seriously and RSPCA assured is acting swiftly to look into these allegations.” The Guardian has contacted the Metropolitan police and the Philip Mould gallery for comment.