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Train services are expected to be disrupted until 9pm tonight, following delays between London Euston / Clapham Junction and Milton Keynes this morning.
Safety checks being made on the line between Hemel Hempstead and Watford Junction mean trains are having to run at a reduced speed between Milton Keynes Central and London Euston / Clapham Junction.
London Midland and Southern railways are no longer affected by this, but Virgin Trains will run a reduced service between Manchester Piccadilly / Birmingham New Street and London Euston.
Passengers may be delayed by up to 20 minutes.
Commuters in and out of London's Euston station are facing delays of up to 45 minutes until midday as a result of safety checks on the line and a signalling problem in the Milton Keynes area.
According to the National Rail Enquiries website, checks are being made on the line between Hemel Hempstead and Watford Junction which means trains running at slower speeds between Milton Keynes Central and London Euston / Clapham Junction.
There is also a signalling problem near Milton Keynes Central.
Until noon, Virgin Trains will run a reduced service between Manchester Piccadilly / Birmingham New Street and London Euston.
No Southern trains will run between Milton Keynes Central and Clapham Junction and a reduced service will run between Shepherds Bush and Clapham Junction.
London Midland have halted London Euston to Tring services. Alternative services will make additional stops at Apsley and Kings Langley.
Commuters in South East London are bracing themselves for travel disruption as major changes to Southeastern services begin today.
Southeastern's Charing Cross trains are no longer calling at London Bridge until August 2016 as the next stage of the station's £6.5bn Government-sponsored Thameslink Programme gets underway.
Passengers who need London Bridge will have to catch a Cannon Street service or interchange enroute.
Charing Cross services to and from New Cross, St Johns, Deptford, Greenwich, Maze Hill and Westcombe Park will be permanently diverted to and from Cannon Street.
There will also be fewer peak trains - two fewer trains in the morning and four fewer trains in the evening peak.
The line will be served by longer trains to boost capacity in peak hours.
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