But in this case that explanation – suicide – didn’t hold up. Having inspected the lake, police divers returned to Warren and his team empty-handed. A body with a slit throat found, but no knife – or other sharp instrument – had been recovered. That, together with the way the blood had fanned upon the water, told Warren the victim had been surprised. He hadn’t been at the water’s edge alone.

For a murderer the park had several advantages. The absence of street lights and surveillance gave freedom of movement to nocturnal visitors; tall trees and boarded-up fences conspired to screen them from the gazes of the outside world. There were multiple entrances and exits, where the killer could have slipped away – one on Herbert Street and Beeches Road, also on Lodge Hill, and another, to the north, on Dagger Lane.

✲

In his previous life Warren had fixed cars. His father was in the motor trade and had apprenticed him at sixteen, thinking, the lad had never fitted in at school. The suburb of Hall Green in the seventies wasn’t the easiest place for the odd and shy to stick out – even someone like Warren, who had a good head on his shoulders. He hated the playing fields – footie and the like – hated being jostled. Whistles, claps and pops rumpled his brow and hurt his ears. He puzzled over the conversations he heard, the turns of phrase, the words that might mean one thing or something else altogether. What was that about? His puzzlement got the better of him and he steered clear of his classmates’ games and maintained a cautious distance. He always had the feeling someone was trying to have him over.

The worst of it were the bullying fists and the insults he always took without a fight. He warded them off with his absence; teachers counted his distress in days off sick. Moving comprehensives didn’t help, only growing up did.

When Warren joined the police at the end of his twenties, keen to work more with his mind, he brought to it, besides a desire to catch the adult world’s bullies, his long experience of cars. Solving injustices was something like repairing cars. A small voice on the phone would report an offence and it’d be like being back at the garage in Digbeth, someone trailing in a Morris Minor that wouldn’t start or a misfiring Ford Escort and nothing else for it but to flip the bonnet and get stuck into the engine, get his hands mucky, track the source of the trouble methodically to some broken part or dingy corner.

With his mind, as before with his hands, he groped his way towards solutions. He familiarised himself with each crime’s make and model and analysed its inner workings. A premeditated act required a certain amount of planning to run smoothly: how to get from A to B, what to wear, where to dispose of a weapon. The nuts and bolts.

The mechanics of a crime, of a murder, were something you could take apart and reconstruct, if you knew how.

His higher-ups liked him; he was meticulous, the way he worked through a case, taking his thinking home and returning from the weekend with possible solutions or some penetrating insight. Working all hours, he wasn’t the least bit put out. He was a man of simple pleasures. Also of strong tastes – curry, the spiciest ones, and coarse pipe tobacco – because he had hardly any sense of smell, which came in handy when you crossed as many dead bodies as he did.

Even as he climbed the ranks he abstained from office politics, making neither friends nor foes among his colleagues. He’d respond to their ‘Guv?’ with only a brief request they were quick to fulfil. They brought him witness statements to reread, crime scene photos to pore over from another angle; watched his pipe disappear inside his jacket as he rose to leave for an interrogation. Later they could see him outside, heading for his car, his pipe sending up pensive rings of blue smoke.

‘Trilby’s on the case,’ the policemen said to one another, alluding to the brown hat worn by Warren indoors and out, in all weathers. It was a rare day when you saw the detective without his trilby. The snug, narrow-brimmed hat shielded his senses from all manner of glints and creaks and hums: it helped him to think.

✲

Jasbir Singh Bains had been murdered. But murders came in a range of models. Warren and his team dealt with hate crimes and honour killings and eliminations of a rival or of a witness, lethal bust-ups – and these were just for starters. Deaths motivated by envy, vengeance, frustrated lust, and greed – the list went on. Which had driven Jasbir’s killer? Warren asked himself. A model that featured a particular focus on location and timing, swift and calculated. A focus greater than, say, a hate crime usually had; far greater than a bust-up. It resembled more a killing for greed’s sake, which were common enough. Greed iced pity, chloroformed a conscience, stiffened the will to act.

But other than a modest mobile phone, which had vanished, and the £22 found on him, the dead man had possessed nothing, it seemed, for an aggressor to steal.

Balwinder Singh, Jasbir’s cousin and employer, reported being the last person to have seen him alive. The cousins had grown up together, and lately Jasbir had been working as a machinist in Balwinder’s firm.

‘They are going to kill me,’ Balwinder said.

This was what Jasbir had told his cousin on the evening of the murder, the two men alone and Balwinder trying to settle him down for the night. Jasbir was between temporary accommodations.

Balwinder had given him twenty quid and put him up in a room above the Desi Junction pub on the High Street. Jasbir veered between exhaustion and agitation; he was rambling.

‘About what?’ Warren asked.

‘Something about a young woman. A woman he’d met and made pregnant. The people around her were mad angry.’

Jasbir was afraid for his life. People were after him.

Who this woman or the other people might be Balwinder hadn’t a clue – Jasbir hadn’t made a whole lot of sense that evening.

Had the cousin, by any chance, heard him say anything about a meeting in the park, or anywhere else, later that night? No, nothing about any meeting.

‘I’m going to go to sleep,’ had been Jasbir’s last words, as though to assuage his cousin’s concern. ‘I’m not going to come out now.’ Balwinder had answered that he was right to get his head down; he was expecting him in for work in the morning.

The cousin had left him before closing time.

✲

I’d imagined him for years before I met the detective. Quite unawares, I’d been in search of him for the story I vaguely hoped one day to write: a story of murderous mystery solved by a neurodivergent policeman. I trusted such a person really did exist.

Like many autistic boys – like young Warren, too, as I would learn – following the adventures of one particular famous detective consumed a fair bit of my adolescence. Sherlock Holmes appeared in a variety of forms: in the much-borrowed library books, as well as their adaptation for TV – films and episodes broadcast on lazy weekends and endlessly replayed. I remember the audacious chases, and the smoggy cobbled streets and Jeremy Brett frowning through a magnifying glass as he reasoned his way to the right suspect.

Warren had the pipe and the headwear but he wasn’t acting a part, nor was he the figment of any author’s creation. He had been in the force for over twenty years when I learned of him. He had made public appeals in connection with his cases, and more recently given an interview in the regional press. From Paris, where I lived, I accessed this online article about his life and career. It had appeared in the Birmingham Mail three years earlier. The headline said, ‘Meet the autistic Birmingham murder detective: “I see things differently to everyone else.”’

At the time of his interview Warren had not long received his diagnosis, and when I got in touch with him, in mid-2021, it was something he was still working through. He had a hard time answering some of my questions; they awakened memories that could be painful. He was far more used to doing the asking than the answering. And then the long stifling summer came – both to Paris and Warren’s rural village in North Warwickshire – and almost shut down our conversation for good. It was the summer Warren’s father was taken to a hospice and his horse Tom – Tom A Hawk – died. There were worse things for a horse (or a father) than dying of old age but that didn’t make Warren’s sorrow any less acute. He had grown up close to stables, near where his parents’ friends owned a farm, and learned to ride saddleless. The instant bond he’d made with the horses had been magical, the connection with another sentient being who would never judge him and with whom the line of communication was always open. Many happy hours of rhythmic trotting jogged his growing brain and exercised his alertness. As an adult, riding Tom A Hawk at the weekend kept him on an even keel.

‘My father and my horse were the closest friends I had,’ Warren wrote to me in a brief and reflective email. He hoped to pursue our exchanges ‘once some of the emptiness has passed’. My heart went out to him, and the writing could wait. I wanted to give him all the time and peace that he might need. But through the wet weeks of early autumn, the colder and shrinking days that were only going to get gloomier, it seemed to me that Warren’s mood might never lift. Perhaps our aborted correspondence had been irremediably tainted by grief.

The weeks of waiting turned to months and autumn to winter. And to top it all off, the Omicron virus cancelled Christmas. In the New Year I contemplated dropping the story. I regretted not happening on Warren’s interview in the press earlier.

Then, just before the spring, our conversation resumed and we swapped emails and video-called over several days. Warren had rallied since adopting a bay gelding he named Rolo. He was self-effacing as ever, preferring to concentrate our exchanges on the victims of homicides he’d helped to solve (and whose every name he could still recall), but he spoke as well about his childhood and his family, about how he got into policing, about the ways in which he and his colleagues thought very differently.

‘Sometimes they’ll tell themselves a story,’ he said. ‘They don’t mean to, but they’ll convince themselves that the person they think is guilty really is. Because this suspect was in the vicinity of the crime at the hour in question and has form but no alibi.’

Colleagues would fall in with each other’s certainty, Warren said. ‘Everything seems to fit, everything points to so-and-so. Some can get pretty wound up if you can’t see how everything points to so-and-so. The CCTV. So-and-so is all over it. Take a look for yourself.’

So Warren would take a look, but something would niggle at him. A problem of logic. The guy takes the scenic route from a crime scene, in the full glare of CCTV? He’s much street-wiser than that. And sure enough, after some further inquiries, so-and-so would prove not to be their man.

‘I suppose I don’t jump to conclusions. I inch towards them. I’m wary of obvious. Obvious isn’t always right.’

We discussed murder in fiction – what TV and novels got right and wrong about it. I was thinking of the story – Warren’s story – I intended to write. I didn’t want to make the mistakes he could at least warn me of.

‘Behind every detective there’s a whole team knocking on doors, chasing up possible leads. Boring leg work, but it’s essential. Without it the detective is nothing. Other than helping with that I’d spend a lot of my time at a desk, mulling a case. Think a middle-aged bloke on his own in his office. Think silence. Not much of the racing about and shouting and other carrying-on you see on the box or read in some books.’

I asked him to describe his most fiendish case and he did so, though there was a limit to how much he could say. For the rest, there were old press articles and other sources of information if I knew where to look.

The Bains case.

The Man in the Lake.

✲

A flummoxed Balwinder, the dead man’s cousin, was talking to the media. He was wearing a black hooded top and a grey baseball cap which he pushed back from his unshaven face for the cameras.

‘Someone must have entrapped Jasbir. I think he was in a honey trap, to be honest.’

It was 5 December, a week since the killing, and still the police had no eyewitnesses, no firm leads, no persons of interest. The weather was good enough to hold the press conference in the park, around the lake.

The day was clear, the sky azure, and Balwinder’s eyes took the cool sunlight without blinking. Behind him the calm lake sparkled. You would never have known that a body had been floating there just a few days earlier.

A picture of the dead man, alive, was distributed to the press. Cropped black hair. A smooth, straight face, above a beige cardigan. The eyes were lowered as if to avoid the viewer’s gaze.

Warren appealed for anyone who had known Jasbir to come forward. He needed to learn as much as he could about his background, whom he associated with, what he did with his time and where he went. A radio journalist’s microphone was recording, a TV man was filming, and a pair of reporters filled a page of their notepads as the detective spoke.