There's disruption on First Great Western services between South Wales and London Paddington because of a signalling problem at Slough.
London Underground are accepting tickets for reasonable routes.
Tickets being accepted on via reasonable routes on other National Rail operator services.
Passengers are advised not to attempt to travel via this route. Disruption is likely to continue until around 10:00am.
All services between Neath and Port Talbot Parkway are suspended due to a line-side fire.
First Great Western, which runs services between South Wales and London, is promising improvements after it was given a 23-month extension to its franchise.
The UK Government says it'll carry on running the Great Western main line until September 2015 before bidding starts for a new long-term franchise.
Greater wifi coverage and additional sleep carriages are among the improvements announced.
There are delays of up to 40 minutes on First Great Western between Severn Tunnel Junction and Newport because of a signalling problem at Severn Tunnel Junction.
Repetitive on board announcements on trains in the Thames Valley will be scrapped after years of passenger's complaints.
First Great Western are retraining one thousand staff to keep their messages to the point after the company's research showed their excessive guard announcements were causing customers to switch off.
First Great Western have decided to reduced the number of announcements made on train journeys, following pressure from passengers. Research carried out by the train provider found, half of passengers don't listen to them.
A spokesperson for First Great Western says the company is 'extremely disappointed' that union workers are planning industrial action later this morning.
The planned industrial action follows a dispute over a colleague's dismissal from the company.
Swansea train managers are due to stage a 24-hour strike later this morning over what they claim is the unfair dismissal of a colleague.
Transport union RMT says the former First Great Western train manager was sacked following an incident that took place when he was off-duty, despite '30 years of unblemished service'.
RMT says First Great Western's response was 'draconian' and 'over the top' - but the company says the former employee's behaviour was 'unacceptable'.
First Great Western says services will not be affected by the planned industrial action.
The Welsh Select Committee say it is 'disappointing' that Wales has so far been excluded from plans for high-speed rail.
But the committee's chair David Davies said that the UK Government's decision to extend electrification to Swansea and the Valley lines into Cardiff should be welcomed.
In a report published today, the committee said that current plans for the HS2 link could cause damage to the Welsh economy by attracting businesses and people to move across the border.
The MPs want the UK and Welsh Governments to develop plans for a high-speed rail link between Wales and England.