Overhead line problems at Watford Junction have caused disruption on London Midland Services from Hertfordshire to London and Southern Trains between Milton Keynes and the Capital.
Disruption is expected to last until around 9am.
There are 20-minute delays on London Midland and Southern rail services between Milton Keynes Central and Watford Junction and on Virgin Trains between Milton Keynes Central and London Euston due to signalling problems between Milton Keynes Central and Bletchley.
Delays of up to 45 minutes on Southern Trains between Clapham Junction and Milton Keynes Central due to earlier faulty train at Willesden Junction.
Tickets being accepted on c2c, First Capital Connect, First Great Western, Greater Anglia, Southeastern, South West Trains, DLR, London Underground and local bus services.