Faster trains between Cardiff, Bristol Parkway and London could arrive next year – if a new train operator can overcome opposition to its plan.
Grand Union has applied to run hourly trains between Cardiff and London, cutting the current journey time of around two hours to one hour 45 minutes.
GWR currently has a monopoly on the route.
On its application to the Office of Rail and Road, Grand Union says that the first train of the day would depart from Cardiff Central at 6.35am, arriving at London Paddington at 8.20am.
The corresponding existing train on GWR leaves nine minutes earlier and arrives 12 minutes later.
Grand Union says passengers will be able to buy tickets on the train, and anyone without a seat will get a 50 per cent refund.
Grand Union says the time saving would come about by cutting out stops at Swindon and Reading. But trains would still call at Newport, and at Severn Tunnel Junction.
The plan is to use old electric trains displaced from the East Coast main line by new “Intercity Express Trains”.
The older trains have a driving van trailer (DVT) which is expected to be used for urgent freight. “This may also include refrigerated space for the rapid movement of NHS biological items,” says Grand Union.
But the Department for Transport (DfT) has argued strongly against the plan, saying its is “highly likely that the service will abstract considerable revenue from franchised services” connecting Bristol and Cardiff with London.
The DfT also criticised the planned rolling stock, hauled by Class 91 locomotives, because of its “relatively poor acceleration characteristics”.
It says: “Any decline in performance on the line as a result of the proposed service could have consequent implications for the revenue and economic stability of franchised services.”
There are also concerns that passengers from further west in Wales will add to crowding on local trains if they decide to change trains at Cardiff to save money.
Grand Union says: “The Welsh Government supports the proposal and has forwarded a letter of support to a number of institutions.”
Transport for Wales has applied to run competing trains on another GWR route, connecting Swansea, Cardiff and Newport with Bristol Temple Meads.
A GWR spokesperson said: “Working with our partners we have transformed services on the Great Western network over the last two years with the introduction of brand new Intercity Express trains enabling a 25% increase in seat numbers, with better punctuality and reliability.
“Our new timetable in December will improve on that even further, with faster services with more seats providing 30 per cent more high speed services than we do today.
“In that context, Grand Union’s current proposals seem disappointing, with the 1980s-era 225s offering no real journey time savings for customers, and significantly fewer seats than GWR’s brand new Intercity Express Trains will already be providing. GWR will have been offering three peak trains an hour from Cardiff to London for over a year.
Grand Union’s announcement follows a demand by Virgin Trains to run trains on the West Coast main line between London Euston and Liverpool.
Sir Richard Branson’s train operator has been disqualified from continuing its franchise after 2020.
The Office of Rail and Road says: “We ensure the passenger and freight train operating companies have fair access to the rail network – and that best use is made of capacity.”