Country diary: The king of butterflies on a bungalow bin lid | Nicola Chester

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Inkpen, West Berkshire: I'm stunned by the sight of a purple emperor down here, as ragged as it is regal. I'm taking it as a good sign

I'm leaning on the lid of Mum's compost bin in a sunny spot, waiting for her to come home, when there is a "plop" by my elbow. A butterfly has landed. There is no gap between seeing the butterfly and recognising it as a male purple emperor. I check the bin scene in disbelief: keys, glasses, phone, His Imperial Majesty (as he is known to admirers). Ragged and abraded of scales, his wings are swathed in royal purple light. A starry Disney wizard's cloak.

He turns, loses his gilding in the new angle of light, and becomes reminiscent of a dusty armchair. The loose constellations on his raised forewings and the crescent of white, messy-edged darts look as though spray paint has bled from under a stencil. On one hindwing is a single tortoiseshell eyespot; the other has been torn away in nips and thorn tears. If this is a king of kings, he is a raggedy one.

I pick up my phone to photograph this extraordinary visitor. Purple emperors feed in treetops, on sap and honeydew, only descending for salts and minerals on rotting things and animal dung. It's been a (relatively) great year for butterfly numbers, but even so.

This is my third incidental encounter with His Imperial Majesty. The first floated on to rudbeckia flowers when I was on the landline to Mum 17 years ago, exhausted with three young children and with 200 miles between us. Now she is in the village, and shortly we'll be moving in alongside her. My second purple emperor was on a towpath dog poo. A runner paused to see what I'd found and I pointed in delight to a suddenly vacant pile of excrement.

It seems inauspicious that such an elusive, aristocratic butterfly should be photographed on a bungalow bin lid. But I choose to claim this as the opposite: a sign that all will be well here at Mum's, a mile from our home of 21 years where I saw my first.

Finally, the butterfly powers away, as if he has torn free from the pins and dust of a Victorian collector's display cabinet.