A knife-wielding man has been detained on suspicion of attempted murder near the seat of British government in London's Westminster.
The unidentified 29-year-old man was arrested at around 8.50am on Monday morning on Horse Guards Parade.
The parade ground, site of the annual Trooping the Colour ceremony, is just behind the prime minister's residence on Downing Street and Whitehall, the road where government ministries and departments are headquartered.
The Metropolitan Police said the suspect was tasered by officers and restrained. No injuries were reported.
The man was arrested on suspicion of attempted murder and possession of an offensive weapon. He was in custody at an un-named central London police station as of Monday evening.
"An investigation is under way," a police spokesperson said. "Met officers will continue to liaise closely with the Ministry of Defence Police as it progresses."
The famous Trooping the Colour tattoo, where the royal Guards regiments parade in their full ceremonial regalia and bearing their battle standards, is held in honour of Queen Elizabeth II's official birthday every June 2.