Passengers are facing severe delays on five Tube lines on Monday morning, including on routes to Heathrow Airport.
Transport for London said there were severe delays on the Piccadilly, Victoria, Circle and Hammersmith and City Lines.
In addition, the Overground was part-suspended from Gospel Oak to Barking Riverside, while the District Line was part-suspended between High Street Kensington and Edgware Road.
The Piccadilly Line disruption was caused by a signal failure at Holborn, while a signal failure at Highbury & Islington hit the Victoria Line.
Disruption at Hammersmith and City and Circle Lines was caused by a broken down train at Edgware Road, which has also severely delayed Metropolitan Line services.
Earlier on Monday, commuters were hit by delays on the Elizabeth Line due to another faulty train, but this has since been resolved.
For the latest travel updates scroll down.
Severe delays on several Tube lines
10:06 , Josh Salisbury
A broken down train at Edgware Road has caused severe delays on several Tube stations.
The Circle, Hammersmith and City, and Metropolitan lines have all been affected, while the District Line is part-suspended.
Meanwhile, both the Victoria and Piccadilly Line have also been hit with delays due to signal failures at Highbury & Islington and Holborn.
Elizabeth Line disruption to continue until 10.30
09:21 , Josh Salisbury
Lines have now reopened following a broken down train between Acton Main Line and London Paddington on the Elizabeth Line.
Whilst service recovers, trains running between Ealing Broadway and London Paddington may still be cancelled, delayed by up to 20 minutes or revised, National Rail says.
Disruption is expected to continue until 10.30am.
Crash near Cockfosters Tube partially blocks road
08:42 , Josh Salisbury
A crash near Cockfosters Station Tube station has partially blocked Cockfosters Road.
Motorists are being warned of around a mile of slow traffic and congestion to Trent Park.
Heathrow Elizabeth Line disruption to last until 9.30
08:26 , Josh Salisbury
Disruption on the Elizabeth Line is expected to continue until 09.30.
Lines have now reopened following a broken down train between Acton Main Line and London Paddington, National Rail says.
Whilst service recovers, trains running between Ealing Broadway and London Paddington may still be cancelled, delayed by up to 20 minutes or revised.
Victoria Line also hit with severe delays
08:23 , Josh Salisbury
The Victoria Line has severe delays due to a signal failure at Highbury & Islington, TfL says.
London Buses, London Overground, Great Northern, Thameslink, Greater Anglia and South Western Railway are accepting tickets.
There are also minor delays on the Bakerloo Line between Queen’s Park and Elephant & Castle due to train cancellations.
Severe delays on trains to Heathrow
08:19 , Josh Salisbury
There are currently severe delays between Paddington and Heathrow Terminals / Reading on the Elizabeth Line.
There are also minor delays between Abbey Wood and Paddington due to an earlier faulty train.
On the Piccadilly Line, there is also severe delays between Cockfosters and Heathrow Terminals due to a signal failure at Holborn.