A man was arrested outside Buckingham Palace on Tuesday after allegedly throwing items – suspected to be shotgun cartridges – into the palace grounds.
Officers detained the man at about 7pm after he approached the gates of the palace in central London.
He was held on suspicion of possession of an offensive weapon after he was searched and a knife was found, but he was not carrying a gun, the Metropolitan police said.
Cordons were put in place after the man was also found to be in possession of a suspicious bag, the force added. Roads have now reopened and most of the cordons have been lifted.
Specialists attended and after an assessment a controlled explosion was conducted as a precaution.
Ch Supt Joseph McDonald said: “Officers worked immediately to detain the man and he has been taken into police custody. There have been no reports of any shots fired or any injuries to officers or members of the public. Officers remain at the scene and further inquiries are ongoing.”
The king and the queen consort were not at Buckingham Palace at the time. However, the king hosted Australia’s prime minister, Anthony Albanese, during an audience at the palace earlier on Tuesday.
Police do not believe it was a terrorist incident, and the mental health history of the suspect is being examined. The man arrested is believed to have been acting alone and it is being treated as an isolated incident.
A Metropolitan police spokesperson said: “It is not being treated as a terrorist incident.”
Armed police who guard the palace can open fire if they perceive a threat to the lives of themselves or others. Police said no shots were fired.
It comes amid meticulous preparations for King Charles’s coronation on Saturday at Westminster Abbey in London in a security operation called Operation Golden Orb.
Thousands of officers are being drawn from across the UK for the ceremonial event.
Hundreds of officers will line the route towards Westminster Abbey while plain-clothed police will be in the crowds and snipers will be situated on rooftops.
A no-fly zone in central London will be put into place with drones banned.