In some ways, it’s an affliction. You spend many months fishing like a sensible person, prepared to adapt your technique and approach to match whatever nature throws your way. But then, in late September, you start looking at insectivorous swallows, gulls; even crows on the lakeshore (and mild overcast days), in a different way. Like a caffeine addict waiting for the coffee van to arrive, you scour the water for a drab little insect about the size of a thumbnail – the mayfly dun; or the sub imago of Atalophlebia australis if you want to be pedantic.

Of course, being a part of nature, dun hatches in the central highlands of Victoria are unpredictable. They can start as early as late September, and as late as mid October. One year, God help us, they hardly happened at all. And it’s important to distinguish between the appearance of duns, and a proper hatch. The former can occur weeks before there are enough duns to get the fish up and interested. False prophets.

The latter – the true hatch – is simple to define: you don’t have to look for individual duns. They’re just there, either surfing the waves, or accumulating like tired ice rink skaters in the oily slicks and eddies behind points and steep shores. This is an incredibly exciting spectacle for flyfishers, but don’t break out the celebratory hip flask yet. You can get duns and no rises – an enormous and seemingly illogical frustration, but again, that’s nature. The most bitter irony is the mega-hatch: duns every square foot across dozens of hectares for hours on end… yet hardly a rise. Have the trout filled up, or are they simply gorging on the ascending nymphs out of sight?

Often, you can do very well in this situation fishing a pair of skinny brown nymphs subsurface. But part of the dun hatch addiction can be the desire to watch your big fat dry fly being clipped off the top as one in a row of real ones. Stupidly, fishing nymphs – something you would have done gladly a few weeks earlier – now feels like… if not cheating, then like a cup of decaf. Not quite right.

To the practicalities of getting the best result, and one of the problems stemming from decades of dun addiction, is how tidy theory slowly turns into layers of exception and outliers. (How simple things seemed in those first few bright-eyed mayfly years!) I could now write for pages about the merits of various patterns and shades of brown or claret, conditions to look for, lake X versus lake Y, etc. But look, there’s a hazy overcast sky, the wind is gentle, and it’s 15C, heading for a top of 19C. I should be, no I need to be, on the water by 12.30pm.