The Knepp Estate in Sussex lies just south of the town of Horsham in the midst of the gently rolling low wield. It has attracted much attention from conservationists across the country in recent years due to an experimental and ambitious rewilding project that has been in place for over a decade. This project has seen the release of herds of free-roaming large herbivores such as longhorn cattle and pigs, boundaries and pesticides have been done away with and much of the land has been steadily reclaimed by nature. As a result Knepp is now a fantastic place for wildlife of all sorts and earlier this week my mum and I went searching for one of the estates most special residents.

Finally summer seems to have arrived; the sun is radiating proper heat from out of the cerulean sky, the green of the oak trees has deepened almost to black, the grass is hissing with insect life and the air drips with pollen. We get out of the car and walk down a green lane, the lane eventually turns into a track running along a mature hedgerow, here we stop to look at a hammer-pond. This old, serpentine lake is full (no surprise) and brimming with life – sedges and rushes grow lushly around the edges, blurring the boundary between the lake and the land. Pond weed and lily pads dot the surface and the banks are hidden beneath oaks and willows that bow out over the water, brushing the surface with their leaves. Great-crested Grebes, Mallard and Coot are milling about among the water plants and Swallows swoop above, scooping flies into their gullets with enviable agility.

We enter another field lined with thick, ancient hedgerows out of which mature oaks grow and hidden Blackcaps warble in stuttering bursts. Black twists of feathers are gliding above the trees – Swifts – then rushing from out of the blue sky on flicked-back wings comes a large swift-like form. As it approaches us its rapier-thin wings are clutched tight to its side as it falls into a high speed stoop; it plummets towards the ground at 45 degrees, straight at the scattering Swallows. It brakes at the last second and veers off, showing its graceful, streamlined body before disappearing as quickly as it had arrived over the next field. A thrilling encounter with a deadly predator – for it was a Hobby, Falco subbuteo.

We now turn along another footpath running alongside an impressive hedge, full of various shrub species and wildflowers and at least 4 metres wide at the base. Meadow Browns and Ringlets are bouncing through the long grass of the meadow, their brown and dusty orange colours mirroring the stalks and seed-heads of the grasses. A Whitethroat briefly flutters over the hedge, then further along a large butterfly rounds a young oak and comes towards us with a distinctive flap-flap-glide flight style. It rapidly glides past and up and over the hedge, never to be seen again, however the white wing markings on a dark background give it away as a White Admiral – an uncommon and very pretty species.

We stop in front of a line of very tall, mature oaks to watch in hope for our main quarry, I spot a swarm of honey bees clustered on a branch at the top of one oak, they remind me of the old country saying ‘A swarm of bees in July is not worth a fly’ – though I have no idea what this means. After some squinting we manage to espy a number of very small butterflies rapidly fluttering around the upper canopy of the oaks, through my binoculars I can make out one that has landed as a Purple Hairstreak. These are a prettily marked species which is not uncommon but difficult to see as they rarely come down from the very tops of oak trees, the males have a wedge of purple colouring on their forewings.

We head back the way we came in and decide to stop and stare at an oak that we passed earlier, perhaps, just perhaps this one will hold the Emperor of insects. After a few minutes with some false alarms from Purple Hairstreaks my mum spots a slightly different flying insect flapping very high up in the old oak. I can see it through my binoculars but I am unsure at first, before realising there is nothing else it could be – the white dots and stripes on the wings, the large size, the way it is gliding frequently and the situation all confirm that it is indeed a Purple Emperor butterfly.

The closest it got – look at that wing!

Over the next fifteen minutes we watch as at first two of these regal Lepidoptera cruise around the oak canopy, then a third appears and is harried off rapidly by (presumably) the male, then at one point no less than four are seen at once. They are quite energetic butterflies, seeing off any passing fly or bug and on several occasions flying down into some nearby willow scrub, they fly all around this large oak from the very top to the lower branches – giving amazing views. One eventually lands and basks in the sun on a low branch long enough for me to get a record shot, I can see its marvelous orange and white marbled underwings and in flight I can glimpse a hint of the purple sheen that gives it its name.

This legendary butterfly has a patchy distribution across southern England, while not super-rare it is scarce enough to cause your pulse to race and it is not easy to find unless you know a regular breeding site. It is not only one of our prettiest butterflies, it is also our largest (female wingspan up to 9cm) and most tenacious, exhibiting strong territorial instincts; males will vie for position on a ‘master tree’ (almost always an oak) during its short flight period of July and early August. The larval food-plant is Goat Willow so this butterfly needs large blocks of broadleaved woodland with willow scrub under-story. If you haven’t guessed this was my first ever sighting, I was extremely pleased to find the Emperor myself and in my own county.