BT are currently experiencing a Serious Incident to their network which is impacting the 21CN ADSL broadband service in the London area. They are investigating the incident and aim to restore service as a matter of urgency.
Currently there is no estimated time to resolution.
We will update when we have further information.
Swift Internet NOC 
BT have advise that the issue with their “Faraday” node has been fixed overnight, and that normal service should now be restored. If customers are still experiencing connectivity issues, please power off the router for 20 minutes, then re-try before contacting the support desk.