The crooked hands of oaks shatter the sky above my head, leaving only fragments of rich blue, like some great atmospheric jigsaw puzzle. What remains of the sky is whipped by watercolour clouds, burning white in the midsummer sun. The leaves of hornbeams and willows have filtered the light into a forest-green mosaic by the time it reaches the floor.

As I gaze up at the canopy, a ragged shape floats weightlessly through the mass of ancient branches. Its wings are ashy, but straddled by a broken snow-white bar. The shape is reminiscent of a shred of paper, so fragile, as it tumbles downward. But with each subtle and shallow flick of the wing, it is propelled forward in a great soaring arc, with effortless power and grace. In but a few seconds, the butterfly weaves back through the oaks and service trees - dissipates into the heat haze, once again merging to become part of its ancient woodland scape.

The view may have been fleeting, but that image has since been burnt into my mind, as it was the first time I saw a purple emperor.

Ancient woodlands are few and far between in the UK, with many of our wild places having been sacrificed to make space for monocultural crop fields. Foxley Wood is a shining beacon, a safe haven, to preserve some of our most precious invertebrate and plant life. From butterflies to bluebells, all manner of localised, endangered species are hosted by this special nature corridor. I only have time to introduce you to a tiny fraction of the site's huge biodiversity, but I beg you to take a visit. You will be immersed in a cryptic realm of natural beauty.

By early May, spring has torn away the last remnants of winter's great cloak, and the forest is in full bloom. A carpet of bluebells, drizzled with sunlight, sweeps across the woodland floor. Scattered amongst their drooping mauve heads are early purple orchids, bringing a shock of contrast with their gaudy scarlet dress. A plant steeped in myth and legend, early purple orchids were said to grow at the base of Christ's cross at the crucifixion. Their burgundy-spotted, fleshy leaves represent drops of Christ's blood, giving them the nickname 'Bloody Butchers'.

In the darker parts of the wood shaded by dense vegetation, the 'windflower' or wood anemone thrives. Each plant bears a single, pink-flushed white flower head which bobs hypnotically when met with even a light breeze; its stem encircled by frail leaves lobed like gecko-toes. Its taller ornamental counterpart, the Japanese anemone, is an abundant feature of many gardens across the country. However, our own native species is a far more vulnerable denizen of only ancient woodlands. Foxley is an important refuge, meeting the criteria of the wood anemone’s increasingly scant habitat requirements perfectly.

Return two months later, and the forest tells a different story. Walk along the entrance track from the car park, and you will be accompanied by the serene thrum of bumblebees. In place of spring's burgundy buds there is now endless verdant foliage. Purple hairstreaks tumble through the branches of oaks, shimmering like handfuls of silver glitter as they fall. Every now and then a male silver-washed fritillary, fuelled by testosterone, whizzes from the willow-cast shadows and over the path in search of a mate. Often the only sign of his presence will be a tangerine flash, but with a closer look the markings are spectacular. Scrutinise the forewing, and you will see bold inky stripes radiating from the thorax. These are known as sex-brands - they emit pheromones which are designed to draw in potential mates.

Cast your eyes up to the canopy, and with luck you may spot a purple emperor, skating nimbly between the oaks. This powerful butterfly is Britain's second-largest, and a very popular target with photographers to say the least! It seems every entomologist's 'bucket list' task is to snap one of these snazzy critters with its deep violet sheen on show. This is easier said than done - the purple colour is caused not by pigment, but by reflection of light by tiny parallel ridge structures in the wing scales known as lamellae. These ridges, formed from chitin, are spaced in such a way that the low- to mid-range visible light frequencies are absorbed by the structures. This means that only the high-frequency visible waves, those rich violets and sea blues, are reflected, and are only visible from very specific angles. The rich kaleidoscope of colour that has for centuries captured the wonder of butterfly-enthusiasts, from Victorian collectors to modern-day naturalists, is in fact just a trick of the light.

While many feel a compulsion to get the 'perfect shot' on the ground, I prefer to watch their behaviour high in the canopy. Purple emperors are fiercely territorial, and have been known to punch well above their weight when it comes to defending their 'patch'! From wasps to warblers, nothing is safe from their aggressive antics. Often the highlight of my summer is watching pairs of conflicting males tumble airily towards the forest floor, so engrossed that the world around them just fades away.

By autumn the leaves have lost their chlorophyll, left as burnt umber husks, whispering tales of cloudless days past. Candlesnuff fungi push through the moss-shrouded coppice, fuelled by winter's first rainfall. The wood echoes with silence. But Foxley has one last spectacle to offer.

Roesel's bush-crickets frequent the open rides and pathways through the forest. Their seemingly endless, churring song is synonymous with muggy September afternoons. When there is warm weather late into the summer, there can be mesmerising mass emergences numbering into the thousands, and one particularly special variant is the winged form. This form is far more common in continental Europe, but with record summer temperatures, more and more Roesel's bush crickets in the UK are developing wings each year. This gives way to the glorious autumn spectacle of great swarms of males taking to the air to find a mate. The presence of this new charismatic cricket in Norfolk is superficially pleasing, but also a constant reminder of the havoc climate change wreaks on our fauna. For each species that colonises new areas, another is pushed to the brink.

For me, no summer is complete without a visit to NWT Foxley Wood. From spring's bluebell carpets to autumn's orthoptera, Foxley offers a huge biodiversity that, within the realm of Norfolk, has no equal.

This article by Oscar Lawrence was first published in Norfolk Magazine.

Foxley Wood is a fantastic place for a woodland walk all year round, with an abundance of wildlife to see. You can find out more about how to visit here.