The Tower of London has been closed following reports of criminal damage to a display case containing the Crown Jewels.
Police said four protesters had been arrested following the incident just before 10am on Saturday.
They said it was reported that food had been thrown on to the case containing the State Crown, which is part of the Crown Jewels, before two protesters left the scene.
"Officers worked closely with City of London Police and security officers and four people have been arrested on suspicion of criminal damage. They have taken into custody," officers said.
"The Tower has been closed to the public while the police investigation continues."
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