Suddenly, it’s drowned out by a far louder noise – the thunder of a train speeding past. Askham Bog feels so wild, it’s easy to forget that it’s a stone’s throw away from the East Coast Main Line and the busy A64 on the outskirts of York.

Much of Yorkshire’s countryside is faded brown or yellow at the moment after months of low rainfall, but this precious surviving remnant of the region’s ancient peatland is lush and green, watered by the legacy of an ancient lake left by a retreating glacier around 17,000 years ago. 

There are splashes of other colours among all the greenery. Guelder rose bushes are festooned with glistening red berries. They’re so implausibly delicious-looking, you can imagine them adorning an exquisite cake in a fancy patisserie. They’re actually mildly toxic to humans if they’re eaten raw, but they make an energy-rich meal for birds and other wildlife.

Closer to the ground, there’s a splash of vivid pink: ragged-robin, with its distinctive frayed flowers, which look as though someone has been methodically pulling them apart. These wildflowers flourish in marshy environments like this and are becoming increasingly rare as Britain’s wild wetlands dry out.

There are other bog-loving flowers too: purple and yellow loosestrife and marsh thistles. Throngs of orange and brown gatekeeper butterflies flutter around them, together with smaller numbers of green-veined whites, peacocks and skippers. 

I find one of my favourite butterflies, a brimstone, reaching with its long proboscis, or feeding tube, to drink nectar from a marsh thistle. It’s hanging from the pink flower with its wings stretching behind it like a cloak billowing in the wind. This pale green one looks like a female; less showy than the yellow male I found feeding on a purple loosestrife flower a few minutes ago. 

It’s a fairly safe bet that, if you focus on a marsh thistle for a minute or two, a pollinator will land on it. I use a macro lens to get a close-up of a common carder bee with a huge black eye and a striking mixture of ginger, yellow and black hairs, finished off with a light dusting of pollen.

There’s another pollinator, a sun fly, buzzing around nearby: its scientific name (appropriately enough in this soggy wildlife wonderland) means “dangling marsh-lover.” 

Migrant hawker dragonflies patrol at head-height, looking for prey. Other insects are harder to spot, their presence betrayed by a quivering blade of grass or a shaking leaf. 

In the dense marshy woodland, I find a curious-looking insect. It’s got light brown wings with black markings, and at first, I assume it’s one of the more than 800 species of moth that can be found on the reserve. Then I notice its body is striped yellow and black, like a wasp’s, and it’s got a red “tail” that looks worryingly similar to a scorpion’s, earning it its name of scorpionfly. It doesn’t sting, though – the tail is used in courtship displays.

I’m starting to appreciate why Sir David Attenborough called Askham Bog a “cathedral of nature conservation.” There are so many insects here that every time I put my rucksack down, I have to check it carefully and remove the spiders and ladybirds that have crawled onto it. At one point, something bigger – I’ve no idea what – scurries through the dense vegetation a metre or two in front of me and vanishes.

As I walk around, I pick up the soft whistles of bullfinches, but they remain well hidden. Despite their stocky appearance and the males’ gaudy, pinky-red breasts, these finches are shy at the best of times. They may have another reason for keeping a low profile at this time of year: birds moult at the end of the breeding season, making them less adept flyers and more vulnerable to predators until new feathers have grown to replace the ones they’ve lost. This means there’s often a bit of a late summer lull for birdwatching.

Some birds do break cover, though: I follow a churring noise, and find a family of wrens flitting about among the scrubby trees. Some of them are fledglings, with the remains of yellow gapes – huge, wide open beaks designed to encourage their parents to feed them – still visible. 

I’m coming towards the end of my visit, and I realise I still haven’t seen one of the jewels in Askham Bog’s crown – royal ferns. 

After hours of roaming round the wild, wet peatland, I finally find one of these enormous plants in the most accessible of places –right next to the boardwalk that runs around some of the reserve. It’s even got its own information board, which tells me that these are Europe’s tallest ferns, growing up to three metres high, and that they depend on water to disperse their spores. 

Royal ferns are hundreds of years old, possibly the oldest living things in York. Like Askham Bog’s flowers and insects, they’re nurtured by this phenomenally rich environment right on the edge of one of Yorkshire’s biggest cities.