Scotland Yard said the arrest of the 31-year-old man, who it did not identify, is linked to "extremist Islamist terrorism."
The force said the man was detained at a London business address Tuesday and remains in custody as officers continued searches today.
Britain's government said earlier this month there has been a substantial rise in the number of terrorism-related arrests including an increase in the number of women and teens detained in 2015.
The national terrorism threat level remains at "severe," meaning an attack is highly likely.