Police conducted a controlled explosion on a suspicious bag the man way carrying as a “precaution”, with it later added the incident was not being treated as terrorism-related at this stage.
"Officers worked immediately to detain the man and he has been taken into police custody," Metropolitan Police chief superintendent Joseph McDonald said in a statement.
"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."
Buckingham Palace said King Charles III and Queen Consort Camilla were not inside at the time of the incident.
The incident came just hours after Australia Prime Minister Anthony Albanese met with King Charles at Buckingham Palace ahead of the King’s coronation this weekend.
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