‘Eighty thousand, Mongol,’ the friend replied.

‘Even better, man. Eighty grand a month. Sweet.’

‘Yeah, right.’

‘All right then, eighty grand a week.’

‘Pffff.’

‘A day.’

Girls, Ayo knew, also had their in-jokes, a sophisticated banter which could be thought far subtler than the boys’, provided, that is, you weren’t the target.

Most importantly, between the teachers and Ayo there existed a mutual appreciation. She liked how what they said in class was clear and to the point, because it came out of their knowledge. She paid them the compliment of listening closely. Her notes were always copious. They’d send their red pen up and down her classmates’ homework, but on hers it almost never landed on an error. How often the Sokales’ television set – turned off or down for a long-distance call to Ibadan – watched her as she lay on the living-room carpet doing her homework.

‘Full stop,’ a teacher would sometimes say. ‘Don’t forget the full stop.’

✲

Outside the air is already warm, and sparkly as you approach the water. Weather as fine as billed in the evening forecast. It has all the makings of the long, dry, peaceful summer days Ayo thrives on.

Before she goes to work, she likes to walk beside the river and have an hour alone with her thoughts. She prefers to hold them back from the people around her, for fear of being misunderstood. Or mocked. Likely both. She tried these thoughts once on her housemate but he could not wrap his head around them. He was for a time far more than a housemate. They met at uni, in Mr Rafiq’s structural analysis class. Although he listened, and forced a straight face when Ayo detailed the lifelike, walking buildings she has sketched many times, he replied in a ribbing way that said that he could not credit them. Even he could not credit them. She learned her lesson; these days, in conversations, she sticks to safer topics. Contracts she has recently managed, budgets calculated, feasibility studies performed. The replacement of a weir in Maidenhead, the design of a fish pass in Oxford. Flood alleviation schemes like the one in Thatcham, a reservoir protecting three hundred homes.

She turns off her street and follows the Thames along the bank, as she has done on many mornings now for years. Every tree and reed is familiar to her, for the route is always the same. As are her brisk, rhythmic movements along it. Here is the patch of grass she always spots coming up at 7.12 a.m. And here is the iron bridge just before half past the hour. In the radiance of the sunlit water she is alive to every passing thought and sight. She feels seen. Seen as she truly is, or wishes she might be. Phil Collins is singing to her from the headphones. Got to love those reverberations.

Downstream of the bridge she enters the building of her dreams, a building in perfect keeping with its environment. Tall, but by no means as tall as it can get. Glass and wood and steel, all proportionate. In the sun the place does more than shine. It gleams. Solar panels, naturally. Lots of windows. Rainwater tanks. No smoke because no chimney. Through the door and up she goes, treading on air, climbing it, each step higher than the last, and she isn’t impeded by the lack of any stairs, for her imagination supplies them. As she strolls beside the meadow now (six minutes long) on the north bank, she continues walking through her mind, taking lefts and rights, from room to luminous room whose scent is of the poplars that she passes, without any thought for the floorboards not beneath her feet, the insulated walls not there, only for the interiors she imagines all kept cosy by the sun, and green with plants. Each room breathes, is airy. When the daylight moves out, the room responds by moving with the sun. The whole building moves according to the time of day – it can twist and turn and stretch. According to the weather, too, including the freak and extreme. Supposing floodwaters surge, the building draws itself up, gradually lowering its rooms, inch by dry inch, as the water subsides. And, what’s more, it would shrink from noise. A flare-up of boisterous traffic, or a shouty crowd. The facade turns away then, or the whole building retreats a few steps, to keep its occupants undisturbed.

But what about the built-up areas? How would her walking, breathing apartments, or whatever they were, have any wriggle room in built-up areas? That was what her housemate wanted to know. He thrust up teasing arms to act out the apartment’s predicament, seeking to elbow itself from a narrow row of terraces.

Ayo adopted a posture of defiance. She wasn’t going to be teased or mocked into conceding. Tomorrow’s towns and cities, she said, would look wholly different. Each place – home and school and office – would be conceived and raised in relation to one another and the surrounding landscape. Residents Hill and Lake and Bird would need to be consulted as scrupulously as anyone else. In which case, given sufficient care and planning and fellow feeling, plenty of space could be found for everyone. No? But by this moment in the argument she understood that her housemate only wanted to talk her out of such thoughts. He was no longer listening. He was waiting. Waiting to rebut. To get her out of ridicule’s way.

These buildings she sees, has seen for years; they are far more real to her than castles in the air. They are, she feels sure, the future, whether hers or that of the world in a century’s time. The question isn’t if but only when.

She sees by the Caversham Lock on her right that it is almost ten to eight. Not long before the route leaves the river and takes her back to her street. A bite to eat, a quick wash and a change of clothes, and she’ll be ready for the day ahead.

✲

In university lectures, Ayo was taught the causes, in addition to the consequences, of flooding. She heard how the recent violent storms of 2012 had wrecked many homes and cost several Britons their lives. Scientists agreed that man-made climate change, if not the sole culprit, was in large part responsible. Picture it, the lecturer said, as greenhouse gas emissions grow, so does the water-holding capacity of the atmosphere. There is also more rain induced from the Atlantic to the British Isles by lower-pressure systems. Ayo pictured the rising waters breaking and entering through somebody’s living-room window, drowning their heavy furniture and carrying off trinkets, letters, banknotes.

It was early on during the same civil and coastal engineering course that Ayo was called up in front of the room and asked to comment on a flow equation. She felt some of the forty eyes – young men’s, almost all of them – watching her. Some perhaps admiring her work, her dedication, while others her blossoming curves and curls, the denim that hugged her narrow waist and which produced in her a sense of being held, of being safe. It was at moments like this, she knew, under a spotlight, that she excelled, when her energy, or intensity, could be regarded with respect and approval rather than considered ‘too much’, as some people said.

‘… and here we can see that the imaginary part of the wave number is zero …’

The spotlight wasn’t confined to university. It shone on her more brightly still when, before that year was out, she entered a local beauty pageant and won. She’d worked hard for her place and wanted to, counting calories and putting in the sweaty hours at the gym. Resolution and fatigue powered the pleasure she took in appearing up on stage. The other contestants were just as driven. Inveterate fundraisers, mountain climbers, volunteers. They spoke without apparent irony of preserving the planet, which seemed to be less cuddling koalas than it was picking up litter. They delivered their thoroughly prepared answers to the judges’ questions, of the kind: ‘Who is your role model and why?’ When it was her turn to face the panel, Ayo remembered to slow down and not to speak so fast. She remembered her mother’s complaining of the headaches her torrents of words and ideas could bring on. Anyway, this was only one part of the contest. What she longed for and dreaded lay ahead: the walk. But even in high heels she did not wobble. Like each of the young women, she had been well rehearsed. A severe voice – ‘no, no, no’, ‘yes, more like that’ – had put them through their paces. The bikini pinched her thighs and bottom. She breathed easier during the evening-wear round, which was of a piece with the hotel’s ballroom. In a pink and silver dress with sequins, a tiara in her hair, feeling like a Bollywood princess strutting her stuff, Ayo dazzled.

Miss No-Mates had become Miss Plymouth.

Plymouth was a good choice for her studies (it had been that or Manchester, which she concluded might be too loud, too manic). A port city with expertise in all things marine, and numerous links to engineering. Also, and as importantly to Ayo, the city was a five- or six-hour drive from Eastbourne. She had reached an age where it felt urgent to leave the parental home far behind, since to leave was to grow up, and the further she went, the more grown up she might become.

It was during her studies in Plymouth that Ayo saw a dyslexia specialist. She was sent after a professor, not an unkind but an insensitive man, on reading one of her papers asked whether English was her first language. It happened that the specialist she was sent to see wanted to assess her for something else besides dyslexia. Autism.

She was, and she was not, surprised.

✲

Another tab on Ayo’s phone is no stranger to her fingers. It takes her to a page in the Encyclopedia Britannica that she began reading in Plymouth, when, far away from her parents and her Christian upbringing, she could explore the beliefs of her ancestors. Water, they taught her, is power, female power. The article she rereads is on Oshun, river divinity, goddess of fertility:

‘The Yoruba people believe that the orishas were sent by Olodumare, who is considered the Supreme God, to populate the Earth. Oshun, being one of the original 17 sent to Earth, was the only female deity. The other gods, all male, failed at their attempts to revive and populate the Earth. When they realised they were unable to complete the task given to them by Olodumare, they tried to persuade Oshun to help them. Oshun agreed and brought forth her sweet and powerful waters, bringing life back to Earth and humanity and other species into existence.’

✲

A wintry Friday, Ayo journeyed the width of the southern coast by train. Friends from last year’s graduation class were waiting for her in Penzance, yet she spent the whole trip having second thoughts. She ought to have told them no. Thank you, but no. I can’t. She had tried texting so, to begin with. London to Penzance would take a morning, and the return a long, tiring evening; she would be on the train twice as long as with her friends; it was simply too far to go for a day trip. But there had been some insistence from the friends, notably Tom, Tom being the one with the handy car and the gran who lived at Land’s End – that and the rare loan of his parents’ cottage for the weekend. Since Ayo’s schedule would not stretch to a weekend, and she’d never had much of a head for excuses, she’d said yes to Friday. A timid yes. She fidgeted in her scratchy seat now and imagined the long reviving walk to come along the coast. The cold rain might hold off, the sun might put in an appearance. This image at least was heartening.

When she pulled into Penzance it was overcast and windy but dry.

At Sennen Cove they left Tom’s car by the lifeboat station, near where the waves were crashing against the jetty. The walk was to Gwynver Beach and back along the clifftops. In better weather, on a hot summer’s day, the footpaths frequently teemed with tourists; they would come from miles around on the advertised promise of cool breezes and matchless views. Today the friends were alone. Only nature accompanied them. From time to time banks of low-hanging cloud released gulls. Tom and the three other young men – civil engineering graduates to a T, all trim beards and red anoraks – in whose company Ayo trod a steep path down towards the beach, formed a protective ring around their friend in case she slipped. The wind off the sea brought an ever stronger taste of salt, of freedom, and when they reached the sands and approached the edge of the water the immensity held, mesmerised, Ayo’s gaze.

She felt a new energy deep within her, sparking palpably through her, like the vigorous flash of lightning across a night sky. She felt irresistibly drawn towards the water and its promise of renewal.

The men could not believe their eyes. She was running, racing, to meet the receding tide. No testing with the tip of a toe or finger the temperature of the water.

This was not because she was larking around, or because she wanted to dive in. It seemed stronger than her, this force that had surged inside her, pushing aside her reason, jolting her legs.

‘Ayo!’ shouted Max, who was the most phlegmatic of the group, his voice concerned. ‘Where are you going?’ He was running after her, they were all running after her. She was turning by then, coming back, but the high waves were faster. They immersed her. One moment the men saw Ayo, the next nothing but the roiling sea. Where, where was she? They cast their arms into the water and hauled her out onto the shore, shivering and stunned.

They assumed the walk was over at that point. But she took off her boots, wrung out her socks, and said she was all right to continue. Someone had a spare jumper, and Ayo removed her waterproof over-trousers and looped them onto her rucksack to dry in the wind.

As Ayo squelched along the beach, they asked her why she had chased the wave out so far and put herself in danger.

‘The sea was calling me,’ she said. She knew they would not understand. Nor did she, not entirely, not yet. But she could not suppress a glowing smile.

They returned to Sennen along the cliffs and went for lunch to the Old Success, where a crackling fire was going. One of Tom’s old mates took their orders at the bar.

Warmed up, dried out, everyone then wanted to walk to Land’s End as planned. Was she really certain she could not stay for the weekend, the friends asked Ayo afterwards on the way back towards the car. They were thinking of stopping at Newlyn to ‘nerd out’ at the ordnance datum level and grab some fish and chips. But Ayo was certain. The no was more confident now, it came easily to her. ‘Thank you, I’ve had a wonderful day with you all, but no.’

On the return train the hours rushed by.

✲

I try to imagine

What the water wants.

There’s no knowing