The main railway line between London and South Wales has been closed after a landslide.
First Great Western said the line near Chipping Sodbury, north east of Bristol, was likely to remain shut for several days.
A spokesman said a reduced service would be run to South Wales via Bath and Bristol every hour instead of every 30 minutes.
Network Rail said engineers were at the site of the landslide to assess the situation and restore services as soon as possible.
A spokesman added that the water levels had built up in the area, causing the landslide.
It happened west of Chipping Sodbury tunnel and is causing disruption to services between Swindon and Bristol Parkway, a spokesman said.
An hourly train service will run from London Paddington to Swansea at 45 minutes past each hour. The trains will run over a different route, adding 40 minutes to journey times and will not stop at Bristol Parkway.
Instead, they will call at Patchway, with buses linking the two stations.
The London Paddington to Cardiff Central service which leaves at 15 minutes past each hour, and the Cardiff Central to London Paddington service leaving at 55 minutes past each hour will not run.
But there will be an hourly train service from Swansea to London Paddington at 29 minutes past each hour. These trains will also take an alternative route after Newport station adding up to 40 minutes to journey times after this point. These trains will also call at Patchway instead of Bristol Parkway.
