Thameslink services between St Albans and London are delayed due to a train fault.
A fault on a train between St Albans City Station and St Pancras International means that train services running to and from those stations may be delayed or cancelled.
Thameslink tweeted at 9.18am today that trains may be delayed by up to 15 minutes, cancelled or revised.
It is not known how long the disruption will last.
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