IT IS common knowledge that readers seeking enlightenment — not just angling readers but readers without the remotest interest in the fishy arts — have been turning to this column in droves. Word has got out that this is the place to be for juicy facts and insights about life.

And so quickly to our Revelation of the Month: Thomas Birch, FRS (1705-66), biographer, historian, editor and, if we are to believe it, respectable married man — the same Thomas Birch who published the vast A General Dictionary, Historical and Critical (1734-41), the same Thomas Birch who became the first Englishman to write up the life of Sir Isaac Newton and many others, liked to dress up as a tree.

I am indebted for this arboreal titbit to Eric Williams, of Esher, Surrey. Mr Williams is one of a band of readers who writes in regularly about this and that — although mercifully never, until now, about the other. Mr Williams said that he picked up this important note from the Oxford Book of Literary Anecdotes (OBLA), a claim that I was at first reluctant to check in case it turned out to be false and the facts got in the way of a story. But it is true.

The OBLA says: “Dr Birch was very fond of angling and devoted much time to that amusement. In order to deceive the fish, he had a dress constructed which, when he put it on, made him appear like an old tree. His arms, he conceived, would appear like branches and the line like a long spray. In this sylvan attire he would take root by the side of a favourite stream and imagined that his motions might seem to the fish to be the effects of wind. He pursued this amusement for years in the habit till he was ridiculed out of it by friends.”

Now, we all have our little foibles. I always wear subdued clothing when fishing and have often been looked at askance for the way I bob and weave my way to the waterside, taking advantage of every scrap of cover. I once got myself into terrible trouble when, crawling on my hands and knees to get at a chub under a willow, I became entangled in a young couple grappling in its shade.

My friends and I routinely sneak up behind cows on the bank-side in the hope of casting unseen to our quarry. We know full well that once alerted to our presence, any decent fish will be sent bow-waving towards the Antipodes, towing all hope in its wake. But dress up as a tree? Even in the knowledge that fish such as chub will come close to trees so that they can gloop down the bugs that are forever falling from them? Hmm.

Although the questions pop and fizz like fireworks, the OBLA answers not one. We are not told whether the doctor preferred to dress as a willow or an alder or, for that matter, a birch. We do not know whether he adapted his suit to match the season. We are left to guess at the indignities visited upon him by dogs and the like.

But it is when we come to motivation that the imagination runs riot. Was it, for example, a rush of blood, some “moment of madness” that caused Birch suddenly to branch out — or was he long in the grip of some secret and unhealthy compulsion? Did he first start off in childhood, perhaps dressing up as a shrub when his parents were out? Did he then find himself drawn farther along that slippery slope until suddenly there he was, out on the riverbank, brazenly in leaf and not caring who saw?

And what of his catches? Did he fool more fish when he was in disguise than when he was not? If no, why did he persist for years with it in the face of ridicule? If yes, why did his friends not dress likewise so that, instead of suggesting just one chub-attracting tree they could have clustered together and formed an entire coppice? Again, the OBLA is silent.

If there is much we cannot know, there are some things we can deduce. One of them is that Birch was a man without pride. We can know it because the doctor devoted a large part of his life to a biography of Sir Robert Boyle of Boyle’s law fame, even though the great man had rubbished in print the very fish that Birch regarded so highly.

In his Occasional Reflections upon Several Subjects (1665), a product so stupefyingly dull and wordy that it might have been the raw material for his work on the expansion of gases, Boyle included a “Discourse Upon Fishing with a Counterfeit Fly”. In it he used a word to describe fish that any dedicated angler would find insulting. Boyle wrote that fish were silly. I say it again — Boyle wrote that fish were “silly”. Does the blood not boil? Should the red mist not swirl? And yet Birch’s praise of his subject was undiminished.

So there we have it. And what have we learnt this month? We have learnt that Boyle knew as much about fish as he did about nuclear fusion. We have learnt that Birch was not only weak but would have done better to keep his proclivities to himself. We have seen that friends can be unkind, history unforgiving and that readers of The Times are indefatigable in their researches.

Coming soon: plenty more. Coming in December: “Izaak Walton — the truth about the man and his ‘incompleat’ tackle”. You can read about it first, right here.

• Brian Clarke’s column appears on the first Monday of each month