The delays, which began early today (January 19), are affecting services between Stevenage and London, with widespread cancellations, delays of up to 20 minutes, and revised routes expected to continue until the end of the day.
The incident was first reported at 4.17am, and as of 9.08am, disruption is ongoing.
Six train operators are affected, including Grand Central, Great Northern, Hull Trains, LNER, Lumo, and Thameslink.
Routes impacted include Grand Central services between Sunderland and London King’s Cross, Great Northern trains from King’s Lynn, Ely, Cambridge, Peterborough, and other destinations into London King’s Cross, and Hull Trains connecting Beverley and London.
LNER services from across Scotland and the north of England into King’s Cross are also affected, as are Lumo and Thameslink trains.
The cause of the disruption is overrunning engineering works between Welwyn Garden City and Alexandra Palace, which have blocked some lines on the key route.
Trains between Stevenage and London may be cancelled.
A spokesperson for National Rail said: “We strongly recommend you delay your journey until later today.”
Passengers attempting to travel during the morning peak faced severe crowding and lengthy waits.
Some were unable to board packed trains, leading to reports of people being left behind at stations.
Those who do travel are being warned their journey could take at least 30 minutes longer than usual and might require additional changes.
Services have been suspended between Welwyn Garden City and Moorgate, and between Cambridge and Brighton on the Thameslink network.
Other trains running between Cambridge and King’s Cross are making extra stops.
Services usually running between Welwyn Garden City and Sevenoaks are starting and terminating at London Blackfriars.
An hourly service is operating at Hatfield, Welham Green, Brookmans Park, Potters Bar, Hadley Wood, New Barnet, Oakleigh Park, and New Southgate, but these trains are expected to be extremely busy.
Ticket acceptance arrangements are in place.
Passengers can use Thameslink, Great Northern and Southern trains on alternative reasonable routes.
Greater Anglia services between Cambridge and London Liverpool Street are also being accepted.
Passengers can also use LNER services between Peterborough and London King’s Cross.
London Buses, London Underground, and selected Uno Bus services are available at no extra cost.
Holders of valid tickets can travel on Uno Bus routes 242 and 243, which connect Hatfield, Welham Green, Brookmans Park, Potters Bar, Cuffley, and High Barnet for Northern Line connections.
Trains are not being accepted on Centrebus route 305.
Hull Trains and Lumo have advised passengers to travel as normal, but warned journeys may be delayed by around 10 minutes.
LNER passengers can use tickets on alternative operators, including Avanti West Coast, TransPennine Express, East Midlands Railway, and Greater Anglia, on selected routes.
Passengers are being advised to check National Rail Enquiries and live departure boards before setting out.
They are also reminded to keep their tickets and note details of their journey if they wish to claim compensation.
Commuters and leisure travellers alike are being urged to plan ahead and allow extra time for their journeys.
Passengers can use journey planners and live travel apps to monitor the evolving situation and find the best alternative routes.
