I THINK that one of the most rewarding and relaxing of summer activities is bridge-top gazing, particularly if the bridge in question is a quiet footbridge spanning a river.

What makes it so good is a birds-eye view which cuts out any glare from the water’s surface, thus allowing a clear sight of anything under the water as well as on it.

On a warm, sunny day last week I found myself gazing down into Thornton Beck from a footbridge just outside the village.

Long fronds of water crowfoot waved from side to side like lazy, green eels; reflections from surface wavelets danced on the trunk of an overhanging tree and shadows of that same tree’s leaves formed a moving mosaic on the pebbles of the riverbed.

I was on the point of nodding off with eyes wide open, if such a thing is possible, when one of the riverbed shadows caught my attention. It was longer and thinner than the other leaf shadows and moved differently – or rather, it didn’t move at all.

When it did finally shift, ever so slightly, I realised that I was looking at a fish – or more accurately, the shadow of a fish.

The animal itself was hovering mid-water, virtually invisible. Such was the quality of its camouflage that without the bright sunlight creating its dark twin on the riverbed I would never have seen it.

Once spotted though, I was able to focus in on the creature and identify it as a young brown trout, about six inches long. If ever there was an animal with an outrageously inaccurate name it is this one, because there is nothing remotely brown about a brown trout.

As any angler will tell you, a trout seen close-up is a staggeringly beautiful fish, festooned with deep purple and red spots circled with white, on an iridescent gold and silver background. The optical miracle is that this patterning underwater, when seen from above, looks uncannily like dull, brown river gravel.

As their Latin name (Salmo trutta) hints at, brown trout are members of the salmon family or, as anglers know them, game fish.

This label originates from Victorian times when the aristocracy fished for sport but only bothered with the tastiest fish ... salmon, trout and char.

These were declared ‘game’ and all other fish rejected as ‘coarse’ and left for the hoi polloi to catch.

These days, even us peasants get a chance to eat trout occasionally, but the fish that end up on our plates usually originate from trout farms, and these are North American rainbow trout – delicious but not British. The brown trout is actually our only native wild member of the family – lake, brook and ferox trout are all just different varieties of the same species.

Incredibly, even sea trout are just brown trout that decide to copy their salmon cousins and migrate downstream as far as the sea.

During the years that they spend in salt water before returning to breed, sea trout change dramatically. Food in the marine environment is rich and plentiful so the fish grow much faster and bigger than they would in the river of their birth.

They also change colour, losing most of their spots and turning almost completely silver – in fact only an expert can distinguish a big adult sea trout from a genuine salmon.

Some brown trout manage to grow to a great size without heading out to sea. The largest ever recorded in our neck of the woods weighed 7lb 2oz (it was caught in the River Rye and is on display in Marley’s Butchers in Helmsley) while the national record is a stag-gering 31lbs.

How do they manage to get so big? Well, cannibalism helps but mainly they are just wily enough to avoid being caught and consequently able to live a long time.

So, if anyone ever calls you or a loved one an old trout ... take it as a compliment.