This kingdom of mine might cover only twenty kilometres squared, but it seemed at times to span a thousand worlds. From winter to sum- mer, welcoming smiles to grumpy shouts, and from last week’s jaded streets to this long grass, busy with butterflies, where I lay on my back, alone and undisturbed, and enjoyed the warm sun on my face.

Down in the distance I could see the city’s gleaming towers, shim- mering in the midsummer haze. I lay still for a while, listening, hov- ering above myself in my mind’s eye, allowing myself to settle into the grid square and its vibe. I heard birdsong and the hum of a motorway. ‘The language of birds is very ancient,’ wrote Gilbert White in a letter. ‘Little is said, but much is meant and understood.’

Each week I arrived in my grid square with little idea what might capture my interest, but an increased certainty that something would. As with all good exploration, there were hints and hopes about what I’d find, but each square also surprised me.

This meant that if I found a square underwhelming, with little to interest me, the responsibility was likely to be mine. Was how much I saw dependent on how much I looked? Some squares buoyed my mood, while others merely matched it. A boring square wasn’t its fault; it was my fault. I knew that as I struggled lethargically round today’s streets, but I also excused myself on the grounds of illness.

I had sweated and shivered through the night, unable to sleep. In the morning, I went to make myself some toast, but we’d run out of bread. I dragged myself to the shed to do some work, but after an inef- fectual hour of pretending to write this book, I tried to salvage some- thing useful from the day by fetching my camera and cycling out to investigate a grid square.

I sheltered beneath a large field maple tree, reframing my atti- tude to rain. Parking the grumbles and persuading myself instead how gleaming clean all the trees looked. Appreciating the gun-barrel-gran- ite skies. Remembering that a day in the rain is better than a day in the office. That kind of thing.

One of my favourite smells is the air after a storm, the earthy scent of petrichor, from the Greek words petros (stone) and ichor (the blood of the gods). We tend to think that our sense of smell is something to be sniffed at compared with the animal world’s, but we are astonishing- ly adept at detecting geosmin, the chemical released by dead microbes that is responsible for the heady smells of petrichor and pools of water. We can smell geosmin at a level of five parts per trillion – that’s thou- sands of times more sensitive than sharks are to the scent of blood. We may be so sensitive to it because detecting water on the savannah where we evolved was a vital evolutionary advantage.