Delays of up to 45 minutes on First Great Western between Oxford and London Paddington due to problem with lineside equipment at Oxford.
First Great Western advise that a normal service is expected to resume by about 3pm. Also affecting Chiltern Railways and CrossCountry.
More top news
Holly has the latest forecast.
Serious failings at a hospital in Sussex contributed to the death of an elderly patient - who died after drinking cleaning fluid.
They are powerful painkillers bringing relief to millions of people - but there is growing concern over the use of opioids.