Train services on the Moorgate line may be cancelled due to what rail operator Govia Thameslink has described as “vandalism on a train”.
Fewer trains are able to run between Hertford North and Moorgate on the Great Northern route as a result.
On the Great Northern website it says: "We had been advised of a smashed window on one of our Hertford North to Moorgate services. As a safety precaution, the train had to be taken out of service for urgent repairs.
"Due to this, it means we have lost one of the 'circuits' on this line of route. Until the train is fixed and back in service, cancellations will occur on this line.
"Please allow extra time to complete your journey as services travelling between Moorgate and Stevenage via Hertford North may be cancelled.
"Please check your journey prior to travelling and continue to monitor customer information screens prior to travelling.
"Ticket acceptance is in place with the following services at no extra cost to yourselves on Greater Anglia between Hertford East and London Liverpool Street, London Underground via any reasonable route, and London buses between Crews Hill, Hadley Wood and London."
Disruption is currently expected to continue until 2pm.
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