The Cambrian Coastal line runs through mountainous countryside

Rail company Arriva organised six trips last August after a 14-year gap, attracting 2,500 passengers.

Eighteen trips are planned this year over a month from the end of July on the Cambrian Coast Line.

The steam service will run from Machynlleth and Aberystwyth to Porthmadog and Barmouth.

Arriva said the steam service will run from 30 July and 28 August after a two-week period last summer.

The experience proved evocative and many people queued to catch a glimpse of the steam train as it pulled into stations along the route, said Arriva.

West Coast Railway is laying on the steam train again this year which has been operating in Scotland for more than a decade.

'Railway enthusiasts'

Sights along the line include the white sands of the Mawddach estuary and the Barmouth Bridge, Harlech and Criccieth castles and Snowdonia Mountains.

Graeme Bunker, managing director of Arriva Trains Wales, said: "Customers told us last year that you just can't beat the scenery when travelling by steam engine - even those who travel the line regularly.

"I am sure the month-long steam services will draw a large number of visitors and railway enthusiasts to the Cambrian coast, many of whom might be visiting Wales for the first time - but not the last."

Services from Machynlleth to Porthmadog will run on Mondays, Wednesdays and Thursdays with services from Aberystwyth to Barmouth running on Sundays.