Passengers should be aware that a loss of power is causing chaos on the railway lines.
Services are now running again northbound out of London St Pancras which is better news for people travelling towards Hendon, Mill Hill, Elstree & Borehamwood, Radlett, St Albans, and Harpenden.
The northbound line had been completely out of action.
But there are delays of up to an hour.
There are also problems southbound too.
The electrical supply at London Blackfriars has caused the problems as well as a vehicle which collided with a bridge at London Bridge station.
Trains are delayed by up to 60 minutes or revised or cancelled.
Thameslink is warning train travel will be disrupted throughout the rest of today.
Tickets are being accepted elsewhere including on other trains, tubes, and buses, via reasonable routes.
Visit the Thameslink website for more information.
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