"Magic beans?" my Stepmother screeches into the wind, "You traded a crate of my best eggs for a handful of magic beans? Idiot boy!"

She turns in her saddle and cuffs me. In shock I lose my balance and desperately grip the flanks of our feathered mount as I watch the seeds tumble through the murky dusk. A half-dozen crows peel away and dive hopelessly after the mottled beans. I rub my cheek and curse my Stepmother under my ragged breath as I try to imprint the lie of the land far below.

I would be back, I swore: to prove that Jack is no fool and that those were no ordinary beans.

I had not expected it to take me twenty-seven years.

London: that is the name of the place my beans fell. In each scattered place, from the Docklands in the East to the City's glowing, cancerous heart, they have sprouted and now soar high, reaching for the clouds.

If my Stepmother could see them, if she had not already taken her final flight, her stiff body strapped to the back of an arctic tern, she would be amazed. She would have been unable to deny that Jack had been right, after all.

True, they do not look much like the beanstalks I expected, but then they were cast amongst concrete and steel. It should be no surprise that they took odd, mineral forms, growing on such rocky ground. Each one is twisted in its own unique shape, dwarfing the man-made structures clustered at their feet. These are aliens in a City whose highest points had once been the spires and domes of its churches, long since neglected and forgotten.

Standing before the tallest of them, the one the people who live in its shadow call ‘The Shard', I curse my earthbound form. Years ago my Stepmother tired of my diminutive size and, wishing for a more useful beast of burden, or perhaps merely to clip my restless wings, she fed me the dull but nourishing food of humans. I have grown since that flight across the City and now match in stature those who live here, their eyes cast down and away from the monstrous edifice in front of me.

If I wish to claim my prize, to reap the golden fruit that my plants have surely borne, I will need to scale this glass and steel stalk and do so without the aid of the birds whose control I learnt at the stern hand of my Stepmother.

My nerve falters as I stare ever upwards, clutching my feather coat close and rocking back and forth on my heels. The cragged summit is burnished gold as it catches the last of the day's sun, promising treasures even as it seems to crowd towards me, the sheer sides offering no vines to hold, no crevices in which to wedge my hands.

I stamp my feet in frustration. It had been a long, difficult journey to this point, through a land shorn of its wild places, devoid of glades and ancient thickets, the creatures tamed or cowed. Even the songs of birds have been muted by the constant thrum of the machines. There was no quiet, no peace, and now here I am at the chaotic centre, unable to go any further.

"Oy! Birdman!"

A gaggle of young women stand in a queue that snakes around the base of the spire. They are dressed in what passes for finery in these parts, flimsy looking garments with no warmth or sense to them. One, a brassy blonde with an implausibly red feather boa wrapped around her bosom, stands proud of the others, a bold step in my direction. "Are you coming to the silent disco, then?" she calls out.

"Silent... what?" I mutter.

"What's a hen party without a cock?" she asks her motley group of friends as they cackle with harsh laughter. "Flying up there, are you?"

I raise my feathery cape to shoulder height, stretching it out until it tugs at my waist, revealing the full, fragile span. Each feather is a token of avian allegiance, from the smallest wren to the tail feathers of an osprey from the lochs of the far North. But my raiment is wishful thinking, a thwarted hope, a suppressed desire. If there were a way to shrink down to the size I was, to take to the air once more, I would have seized it by now.

"I cannot," I admit.

"Never mind love, we've got a spare ticket. Why don't you come up in the lift with us?" she says, wrapping her fleshy arm around mine, dragging me into the queue.

"Lift?" I echo.

In my time I have seen many things, been places that no normal sized man or woman can ever dream of. I have travelled the oceans on the back of an albatross, spending hours aloft between each beat of its mighty wings. I have flown in a murmuration of starlings that turned the evening sky black, reeling in formation like a cloud. I have thrilled as a falcon cut through the air, its wings folded back, my eyes watering, screaming in heady excitement as it halts its dive a foot above the ground, talons reaching for its prey.

And yet you humans have wonders enough, for all that you so readily turn a blind or jaded eye upon them. We pass through a gleaming corridor and enter one such: a room whose mirrored walls reflect the magical lights and pictures that dance across the ceiling.

The blonde tells me she is called Sharon and introduces her friends, a set of names that make no more sense than their clothing. One, a white veil adorning her head, an image of chastity betrayed by her rouged lips, by naked arms and shoulders and legs, by a large square sign around her neck that bears simply the letter ‘L', offers a limp hand before wrinkling her nose. "What's that smell?"

"Bird lime," I tell her as she backs away.

"Is that, like, bird shit?" she asks, laughing raucously.

I explain the steps that produce the sticky substance by which the feathers are fixed to my winged coat. But I can tell she isn't really listening.

There's an odd, brief sensation, like a pigeon launching itself into the air and, when the doors slide open and we step out, it is not into the same gleaming corridor but into a glass room far above the sparkling City. A marvel to have ascended so high, so quickly, with no obvious agency by which this sorcery is performed. Sharon and her vapid friends appear to think nothing of it, babbling away. Perhaps such miracles must be ignored to avoid crushing fragile spirits and egos.

I wonder how they will cope with the treasures that surely lie ahead, my treasures, for was it not I who sowed those seeds, even by accident? These towering plants and the fruit they bear rightfully belong to me.

But there's no gold, no jewels. Just gaudy baubles that adorn the necks and wrists and ears of the throng of people packed into the open space. They move in tight clusters, their limbs jerking in spasms as though they have been bound by thorns, a discordant cacophony of voices, out of tune and out of step, malodorous and ugly, forced from their unwilling throats.

Sharon hands me a black crown and takes another for herself, resting the glowing ends of the incomplete torc over her ears. Tentatively I do the same and am assaulted by a frightful screeching, by the boom-boom-boom of an approaching demon.

I tear the evil thing from my head, dash it to the floor and cringe away. Sharon starts after me, perhaps to escape, perhaps to rescue me, but she's dragged back into the crowd by her bewitched friends.

"Loser!" they shout.

"Freak!"

I seek refuge at the very edges, cower against the sloped walls of cold glass, but even there the air is stale and close and threatens to smother me. The mirrored room disgorges another batch of victims, the room growing yet more crowded, more frenetic. I look around in mounting panic and see steps leading upwards.

A glimmer of hope then: this is not the top. This level is an obstacle, a challenge to be surmounted, the crowd of writhing people enslaved by a terrible enchantment which protects the treasures above from the unworthy.

The red rope barrier that stretches across the stairway is easily hurdled. I run up the steps, barge through a door that shrieks as though mortally wounded by my passing.

I find myself alone in a deserted eyrie, walled by glass but open to the sky above. The wind flaps the tails of my feathered cloak as I peer down the sloped side, a thousand feet up. From here I can see all of London laid out before me, all the other stalks of concrete and glass and steel that sprouted from the beans I spilt. They glitter, their lights calling out to me and to others, beacons in the darkening night.

But there is nothing here but the view. Even at this lofty height the beanstalk bears no fruit, only disappointment. Are the others the same? Do all who heed their siren call suffer the same cruel fate as those I left below?

Something tells me it is so. That there are no treasures; it is a fool's errand for fool's gold.

I stand looking up at the stark structure, at the giant splinters rising up around me. There are no more steps, no way to climb further and nothing to reach for anyway. A dead end.

Worse, it is a trap: without wings, I will have to descend the way I came. But how to avoid the floor packed with the ensnared, how to channel the powers of the mirrored room to take me back to the base of this diseased and infertile plant?

Impossible. Hopeless.

An old crow alights on my slumped shoulder. Its feathers are gray and mottled, one eye clouded over and the gaze from the other ancient. It peers at me as I raise my finger to stroke its rough flank. Then it hacks and coughs, hacks once more, and spits a slimy speckled bean onto my open hand. The bird nods at the ejected seed and then awkwardly takes flight, the dig of its claws into my arm as it launches into the air bringing me to my senses.

I stare down at the magic bean. If I were to cast it out onto the hard pavements far below, it would, I am sure, take root as the others did and might someday challenge even the rarefied heights of this calcified growth.

But it would remain forever barren, stunted by the thin soil it is forced to grow in. A seed sown in this urban landscape can only grow into another of these tall, sterile growths. It needs sun and rain and fertile ground, things not to be found here.

While I have been lost in thought, the sounds from below have faded. I descend, unsure of what terrors lie in wait.

Most of the victims have gone, who knows where. A few stragglers linger, their sweaty, flushed faces showing the terrible ordeal they have been through. One, I recognise.

"Jack!" Sharon says, bouncing over, shedding tattered red feathers, linking her arm once more with mine. "I thought we'd lost you."

I glance around, still wary. "Your companions?"

"Gone on. We can meet up with them later." She squeezes my arm, looking shyly up at me. "Or not. I didn't mean to freak you out."

Her smile is open and honest and I realise she's the first human I've paid any attention to since my arrival here. I've been focused on the false treasure that was promised at the top of the beanstalk.

For that matter, nor have I eaten, or slept. My stomach grumbles at the thought.

She hears it and laughs. "Why don't I buy you a bite to eat? I can't see any pockets in that get up."

I discretely pat the small down-filled fold that contains everything I own, and that only recently re-acquired, borne by an aged and faithful crow even older than I. A single, priceless bean. But here, on the banks of a sluggish river, hemmed in by stone and brick, where nothing green is natural, not even the grass, it is of no value at all. For now, I am in Sharon's hands, though I do not understand her concerns, her passions, or her technology. I do not understand what it was she sought at the top of The Shard.

Standing close, I breathe in her scent. Beneath the stench of the fake flowers, the acrid sweat, the smell of some noxious potion seeping through the pores of her skin, there are rich hints of earth, of cooling moss and wet leaves and the passage of burrowing insects.

"Where do you live, Sharon?" I ask.

"Forward and cheeky!" she exclaims and then shrugs, leaning heavily against me. "Tonight, I'm staying with Alicia, the bride-to-be, and absolutely no men allowed. Tomorrow, I'm headed home, to my little house and garden in the country, to Kent. You'll have to visit me there, if you want to see me again."

Perhaps I have found something at the top of this beanstalk after all. I run my thumb over the still sticky seed tucked in the lining of my feathered cloak. I think I know now where I need to plant it, to give it the best possible start.

In ancient times, to secure a good harvest, a bargain had to be struck with the land. Blood, to replenish the soil. That is what those other beans of mine lacked: sacrifice.

I can feel the heady warmth from Sharon stood so very close. I'm almost giddy as I imagine my last, solitary bean waking from its long sleep, the splash of vibrant green growing up through Sharon's distended and thinly covered belly, reaching for the sky, the roots travelling the other way, snaking through and beneath her into the fertile earth of her place in the country.

"Tell me, Sharon," I say, reaching for her hand, entwining my fingers in hers, testing her will and her strength, feeling her yield, feeling her desire, "how big exactly is your garden?"