Teams from Scotland, Ireland, England and Wales are taking part in the event
A river heavily polluted by the Welsh coal industry has recovered so well, it is hosting one of the most important fly fishing events in the calendar.
The River Taff at Merthyr Tydfil has been chosen as the location for the Rivers International Fly Fishing Championship.
The competition, which gets under way on Friday, sees some of the best trout anglers in the British Isles take part.
Along with trout, the river has also seen the return of spawning salmon.
In the 1980s, salmon had become almost extinct on the river.
But following two decades of investment, including the installation of fish passes along the river, salmon have began returning to the upper reaches of the Taff.
That has been helped by a decision in 2007 to release 5,000 young salmon in to the river in a bid to help restock the species.
Casting his fishing line from the banks of the Taff, Tony Rees from the Merthyr Tydfil Anglers Association said the changes over the last 20 years have been remarkable.
"It's really great to think that years ago you wouldn't be able to fish this river at all."
Mr Rees is one of the organisers who has brought the fly fishing competition to the Taff.
"We're standing on the bottom end of a bend where the old Merthyr Vale colliery was. At that point there, that's we used to have one of our major pollution outlets, when the collieries were running where the coal dust used to come out at night.
"I did write a letter once to the chairman of what was at the time Welsh Water, and I actually said to him it would be nice to see the fish coming up the Taff with miners' lamps - that was the only way they would have got through the coal dust.
"Look at the riverbed today - it is spotlessly clean."
Angling writer and president of the International Fly Fishing Association of Great Britain, Moc Morgan said when he first suggested bringing Friday's competition to Merthyr "people just looked at me and wondered - 'is this man sane or not?'".
"Well, they came here and they have seen what we can offer in Wales," he added.
He also said he believed the area could play host to the Commonwealth fly fishing competition next year.
"I'll be very, very surprised if it's not based in Merthyr," he said.