FOR the first time in a century a trout has been caught in a London tributary of the Thames, the Wadle. The news would arouse mixed feelings in Richard Jefferies (1848-87), one of our finest nature writers.

Son of a Wiltshire farmer, Jefferies learned to shoot early and as a young man was rarely seen without his gun. Then, one day, as he was about to shoot a pheasant...:

"My finger felt the trigger, and the least increase of pressure would have been fatal; but in the act I hesitated, dropped the barrel, and watched the beautiful bird. The watching so often stayed the shot that at last it grew to be a habit: the mere simple pleasure of seeing birds and animals, when they were quite unconscious that they were observed, being too great to be spoiled by the discharge.''

Jefferies had discovered what the philosopher Albert Schweitzer called "reverence for life". And nothing illustrates this better than his adoption of a wild London trout.

While living in the capital, Jefferies spotted the trout from a bridge over Hogsmill Brook. Only the keenest of observers could have picked out the fish, concealed among waving reeds by a bridge pier. Jefferies returned almost daily and, in a thrilling essay, he describes the extraordinary lengths to which he went to protect "his" trout.

Only when he was unobserved did he peer intently. If others approached he would sometimes turn his back to the parapet. Or he would strike it with his stick, or raise his hat - to send the trout under the bridge. He wrote: "It was a relief to know that so many persons who went by wore tall hats, a safeguard against their seeing anything, for if the shadow of the tall hat reached out beyond the shadow of the parapet it was enough to alarm him the trout before they could look over.''

For three summers the trout survived, even avoiding the hook of the sole angler who noticed him and tried, for three days, to land him. Jefferies even took one or two friends to see "this wonderful fish, which defied all loafers and poachers".

Then, in the fourth summer - disaster. A pipe-laying scheme temporarily turned the trout's haven into a stagnant, muddy pool. Into it, seeking what they could find, waded men - "barbarians'' to Jefferies - with an eel spear. Jefferies couldn't watch. He saw his trout no more, and though he continued to look over the parapet, the stream ever after seemed "colder, darker, less pleasant. The spot was empty, and shrill winds whistled through the poplars".

Of course the pipe-laying that did for Jefferies' trout might have been part of the industrialisation of London that finally banished all trout - until now. The episode reinforced the lesson Jefferies had learned when he refrained from shooting that pheasant: "It is so easy to make the acquaintance - to make friends with the children of Nature. From the tiniest insect upwards they are ready to dwell in sympathy with us - only be tender, quiet and considerate towards them...''

Jefferies has more of importance - much more - to say than this. Little heard these days, his is a voice for our times, as I aim to show next week.