Trains into a busy City of London station have been suspended on Friday morning due to a radio system fault.
The issue, affecting communication between train driver and signaller, means all lines are blocked between Moorgate and Drayton Park in north London.
There is currently no service at the following stations: Highbury & Islington, Essex Road, Old Street and Moorgate.
Disruption is expected until 9am according to National Rail.
Follow the latest updates below.
Travel update
10:17 , Tom PlaceThe issues between Moorgate and Drayton Park have now been resolved, with a normal service resuming on the line.
On the underground, there are minor delays between Willesden Junction and Clapham Junction on the Mildmay Line, with a good service on the rest of the network.
Moorgate issues easing
09:29 , Tom PlaceLines have now reopened between Drayton Park and Moorgate following a fault with the signalling system.
As services recover, some delays are expected, which should be resolved by around 10am.
TfL back up and running
09:27 , Tom PlaceThe TfL app and website appear to be back up and running following a Cloudflare issue.
North Circular delays
09:15 , Tom PlaceThere are currently serious delays on the North Circular near Waltham Forest.
There are queues on the Eastbound from A10 Great Cambridge junction, and Westbound queues from Chingford Road - expect serious delays.
TfL site down
09:08 , tom placeThe TfL app and website are both currently down, along with a number of other sites.
More shortly.
Bromley South incident resolved
09:06 , Tom PlaceThe incident at Bromley South has been resolved, and services will not call as scheduled.
The scene at Bromley South
09:01 , Tom Place
Police incident at Bromley South station
08:55 , Tom PlacePolice are currently dealing with an incident at Bromley South station, and services are not currently calling there.
More as soon as we have it.
Jubilee line delays
08:24 , Tom PlaceAn earlier faulty train at Baker Street has resulted in minor delays southbound on the Jubilee line.
Mildmay line recovering
08:12 , Tom PlaceThe earlier track fault at Kensington Olympia has been resolved, so there are now only minor delays between Clapham Junction and Willesden Junction on the Mildmay line.
Rest of tube running smoothly
08:04 , Tom PlaceThere is a good service on the rest of the underground at the moment.
The disruption between Drayton Park and Moorgate is expected to be resolved by around 9am.
Metropolitan line delays
07:47 , Tom PlaceThat signal failure at Hillingdon means there are now also minor delays on the Metropolitan line between Harrow-on-the-Hill and Uxbridge.
The Piccadilly line is now running again between Rayners Lane and Uxbridge, with minor delays.
Roads are clear
07:38 , Tom PlaceThere’s no serious disruption on any roads around London at the moment - we’ll update you if this changes
What is causing the delays?
07:33 , Tom PlaceWithout radio communications, train drivers may not be able to receive urgent safety messages, or contact the signaller if there's an incident.
The network is designed to function for a short period of time after a failure, but in this case, Great Northern are no longer able to run services.
Great Northern are working with Network Rail, who manage the radio system, to deal with the issue as quickly as possible.
More information on the Moorgate issues
07:24 , Tom PlaceTrains that normally run to and from Moorgate are now terminating and restarting at Finsbury Park or Drayton Park, with some services diverted to London King's Cross
Tickets are being accepted for no extra cost on the London Underground, London Buses, and Great Northern and Thameslink services.
Tube and Overground update
07:11 , Tom PlaceThere are currently severe delays on the Mildmay line between Clapham Junction and Willesden Junction while TfL fix a track fault at Kensington Olympia.
There is also no service on the Piccadilly line between Rayners Lane and Uxbridge while a signal failure at Hillingdon is fixed.
There is a good service on the rest of the network.
