The man, who has not been named by police, was detained on Saturday from a property in east London. He is suspected of the commission, preparation or instigation of an act of terrorism.
While the suspect is in custody, Metropolitan Police officers are searching the property. The Met, who confirmed the man will be held until 4 January, said the arrest is not related to the London Bridge terror attack on 29 November. More to Follow, check back for updates.
Boris Johnson has said that 74 people jailed for terror offences and released early will have their licence conditions reviewed. The Ministry of Justice launched the urgent review after convicted terrorist Usman Khan, who had served half of his sentence, killed two people in a knife attack at London Bridge.
The prime minister claimed scrapping early release would have stopped him. But Labour is blaming budget cuts for “missed chances to intervene”.