The sea trout, revered by anglers for its spectacular fighting prowess and by gourmets for its delicate flavour, has returned to the Kelvin Burn that runs through the heart of Glasgow.

For more than a century the Kelvin Burn was one of the most polluted rivers in the country but, says Jim Smith, chairman of the Kelvin Anglers Association, “Anglers in recent weeks have begun to catch sea trout weighing more than five pounds.”

Last week anglers reported several small salmon that had clearly spawned in a Kelvin pool, the first evidence that the returning salmon are beginning to reproduce.

More than £ 75m has been spent over 10 years cleaning up the Kelvin Burn, which has been plagued by pollution since the days of the Industrial Revolution.