Police have made a "significant arrest" in connection with the Parsons Green terrorist attack.
An 18-year-old man was arrested by Kent Police in the port area of Dover on Saturday (September 16) under section 41 of the Terrorism Act.
The man remains in custody at a local police station, and will be transferred to a south London police station in due course.
Deputy Assistant Commissioner Neil Basu, senior national co-ordinator for Counter Terrorism Policing, 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."
Thirty people are known to have been injured during the attack, in which an improvised explosive device was detonated on a tube train at Parsons Green tube station, at around 8.20am on Friday (September 15).
Detectives from the Met's Counter Terrorism Command are continuing to urge anyone with information about the terrorist attack to contact police.
So far, detectives have spoken to 45 witnesses and continue to receive information from the public to the confidential anti-terrorist hotline.
Members of the public have sent 77 images and videos to investigators through the UK Police Image Appeal website.
Anyone with footage or images from the incident is urged to upload them, where they will be looked at by investigators.
Anyone with information is urged to call the Anti-Terrorist Hotline on 0800 789 321 or, in an emergency, always call 999.
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