Detectives investigating the terrorist attack at Parsons Green on Friday have made an arrest in connection with the investigation, police say.
The 18-year-old man was arrested by Kent police in the port area of Dover this morning, Saturday, 16 September, under section 41 of the Terrorism Act.
The man remains in custody at a local police station. He will be transferred to a south London police station in due course.
Commenting on the arrest, Deputy Assistant Commissioner Neil Basu said: "We have made a significant arrest in our investigation this morning. Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.
The public should remain vigilant as our staff, officers and partners continue to work through this complex investigation. We are not, at this time, changing our protective security measures and the steps taken to free up extra armed officers remain in place.
This arrest will lead to more activity from our officers. For strong investigative reasons we will not give any more details on the man we arrested at this stage."
Earlier, the Islamic State claimed responsibility for the'bucket bomb' attack on the packed underground train at a London station on Friday, injuring at least 29 people.