Four protesters were arrested Saturday after splattering food on the display case of a priceless diamond-encrusted crown at the Tower of London .

The Crown Jewels display was temporarily closed after members of a group called Take Back Power smeared apple crumble and custard - a traditional British pudding - on the case containing the Imperial State Crown worn by King Charles III as he left his coronation ceremony in 2023 and during his speech to open Parliament in 2024.

The hefty crown, containing 2,868 diamonds, 17 sapphires, 11 emeralds, four rubies and 269 pearls, was crafted for the coronation of Charles' grandfather, George VI, in 1937.

Police said the protesters were arrested on suspicion of criminal damage. But the invaluable jewels that are a major tourist draw were unharmed, Historic Royal Palaces said.

The civil disobedience group that advocates for a permanent citizens' assembly and wants to tax extreme wealth said two of its members had thrown the food and two others were also arrested and taken into custody.

The stunt is one of many that has targeted prized treasures and artworks to draw attention to a political cause. Petroleum protesters were imprisoned last year for tossing a can of tomato soup on glass protecting Van Gogh's “Sunflowers” at London's National Gallery. (AP)