A man has been arrested on suspicion of attempted murder after confronting police with a knife in Westminster in central London, not far from the parliament.
The 29-year-old was said to have approached two Ministry of Defence Police officers in Horse Guards Parade at around 8:50 am (local time) on Monday.
Police used a Taser on the man before restraining him and placing him under arrest on suspicion of attempted murder and possession of an offensive weapon.
No-one was injured and the man remains in custody at central London police station.
The incident is not being treated as terror-related, the Met Police said.
The force added it would be working alongside the MoD Police as it carried out an investigation.