A 32-year-old man was arrested on suspicion of being a member or support of Islamic State (Isis), according to the Metropolitan Police.
The Met Police's Counter Terrorism Command raided an address in Newham in east London on Saturday morning.
The man was arrested on suspicion of collecting information which may be useful to somebody who commits or prepares acts of terrorism and encouragement of terrorism, according to Scotland Yard.
Man arrested in #Newham this morning by officers from the Counter Terrorism Command on suspicion of terrorism offences.
— Metropolitan Police (@metpoliceuk) February 14, 2015
An Evening Standard reporter was told by Mark Rowley, Britain's head of counter-terror policing, that UK police were arresting a terror suspect every day.
The man under arrest is being questioned at a south London police station.