Four people have been arrested after custard and apple crumble were flung at a display case containing part of the Crown Jewels in the Tower of London.

Police were called shortly before 10:00 GMT on Saturday after the case containing the Imperial State Crown – which is typically worn by the King at formal ceremonies – was defaced.

The Metropolitan Police said four people had been arrested on suspicion of criminal damage. The Tower’s Jewel House was temporarily closed to the public while the police investigated.

Take Back Power, which describes itself as a new non-violent civil-resistance group, claimed it was behind the act.

The group said it carried out the stunt to demand the UK government establishes a permanent citizen’s assembly – a “House of the People” – with the power to “tax extreme wealth and fix Britain”.

Footage shared by the group on social media showed one protester removing a large foil tray of crumble from a bag before slamming it against the glass protecting the Imperial State Crown.

Another then poured a tub of bright yellow custard on the front of the case.

“Democracy has crumbled,” one protester could be heard shouting. Another added: “Britain is broken. We’ve come here to the jewels of the nation to take back power.”

Meanwhile, surprised tourists could be seen reacting to the stunt.

Historic Royal Palaces confirmed that the Imperial State Crown was not damaged.

The Jewel House reopened to the public early in the afternoon.

This is the second demonstration claimed by the group in the past few days.

On Wednesday, three protesters emptied bags of manure onto the floor of the Ritz hotel lobby under its 25ft Christmas tree.

The Imperial State Crown is a famous symbol of the monarchy and was worn by King Charles III as he left Westminster Abbey on his coronation day in 2023.

Beyond coronations, the priceless working crown is only used during formal occasions, such as the State Opening of Parliament.

When it is not being used, it is kept in the Jewel House at the Tower of London.

It was originally made in 1937 for the coronation of King George VI and contains 2,868 diamonds, 17 sapphires, 11 emeralds, four rubies and 269 pearls and weighs over a kilogram.