Ever since Rachel Helliwell was a kid, she remembers her dad being out on the River Spey with a fishing rod in hand.

He always fished on one particular estate, and after 45 years had got to know the stretch of water pretty well. But the last few seasons have been among the worst in living memory. The Atlantic salmon that once crowded these waters have nearly disappeared.

“He is very sceptical of climate change,” Rachel said. “So when I said it was probably this which was affecting his fishing, he didn’t believe me.”

Record-breaking water temperatures – Rachel is more equipped than most people to make this assessment. As a senior research scientist at the James Hutton Institute in Aberdeen, she has dedicated her career to all kinds of water research.

“I decided to find out what was happening in the water of the Spey which might be affecting salmon,” she said.

“I thought it would be really difficult but actually my dad said that ghillies take various river measurements morning and night each day – I had no idea this was the case.”