Rail services between south Wales and London Paddington have been affected by flooding.
First Great Western say they've had to cut the usual two trains an hour - one from Cardiff and one from Swansea - to just a single train service.
Flooding in the Maidenhead area has severely affected the number of trains getting into London.
Great Western say passengers who do get a train should also expect a delay of around 30 mins.
The delays and cancellations are expected to last for the rest of Tuesday and possible into Wednesday morning.