A second man was arrested on Sunday after three police officers were injured by a man wielding a 1.2-meter sword near Buckingham Palace in central London on Friday.
The 30-year-old man has been arrested on suspicion of terror offences, and a search of a property in west London is being carried out, the police said.
"The man was arrested on suspicion of being involved in the commission, preparation or instigation of terrorism," and "he has been taken into custody," a police statement said.
The arrest was made after a 26-year-old man drove a car in front of a police van in a restricted area near Queen's official residence on Friday evening. The man, who comes from Luton some 50 kilometers north of London, had repeatedly shouted "Allahu Akbar", meaning in Arabic "God is great".
The man was arrested at the scene and remains in custody. Three police officers were slightly injured in a struggle to arrest the sword-brandishing man.
The police force on Sunday obtained a warrant to detain him until Sept. 1.
"This is a timely reminder that the threat from terrorism in the UK (United Kingdom) remains severe," Metropolitan Police counterterrorism chief Dean Hayton said.
The British police on Saturday opened a counterterrorism investigation into the incident, which came as police across Europe are on high alert following a spate of terrorist attacks this year.
In the Britain alone, three attacks claimed the lives of dozens of people, while police in Spain are probing a suspected terrorist network after twin assaults in the northeastern region of the country earlier this month.