National Rail confirmed all services between London St Pancras International and London Blackfriars were disrupted at around 3.30pm today (August 28).
The incident is expected to cause major disruption to Thameslink trains to and from these stations until 6pm.
Failure of the electricity supply is disrupting the southbound line running towards London Blackfriars.
Trains running between these stations may be cancelled, delayed by up to 80 minutes or revised.
Commuters are being advised to delay their journey later in the day or if they are travelling to either Gatwick Airport or Luton Airport, to allow 90 minutes longer than usual to reach their destination.
The following service changes are highly likely, in both directions, until further notice:
Direct services from Bedford to Three Bridges are cancelled.
You can use Great Northern services from King’s Cross to Cambridge as an alternative. Change at St Pancras for a short journey by foot to or from King’s Cross.
Some services will terminate and restart from either Kentish Town or Mill Hill Broadway.
You can travel on alternative Southeastern services between London Victoria and Rainham.
Change at London Kings Cross for a limited LNER services towards Peterborough.
Arlesey, Biggleswade, Sandy, St Neots and Huntingdon will have no service.
