But does that actually matter, he wondered suddenly. Am I already an old fart at thirty-nine? Do I really want this city I love so much preserved, warts and all, in some kind of a time warp?

At this moment, however, he had something bigger on his mind than the Brighton and Hove Planning Department’s policies. Bigger too than the human remains they were on their way to observe. Something that was depressing him a lot.

Cassian Pewe.

On Monday, after a long convalescence following a car accident and several false starts, Cassian Pewe would finally be commencing work at the CID headquarters, in the same role as Grace. And with one big advantage: Detective Superintendent Cassian Pewe was the blue-eyed boy of Assistant Chief Constable Alison Vosper, whereas he was pretty much her bête noire.

Despite what he considered to be some major successes in recent months, Roy Grace knew he was just one very minor screw-up away from being transferred from the Sussex Police Force to the back of beyond. He really did not want to be moved away from Brighton and Hove. Or, even more importantly, from his beloved Cleo.

In his view, Cassian Pewe was one of those arrogant men who were both impossibly good-looking and fully aware of it. He had golden hair, angelic blue eyes, a permanent tan and a voice as invasive as a dentist’s drill. The man preened and strutted, exuding a natural air of authority, always acting as if he was in charge, even when he wasn’t.

Roy’d had a run-in with him over just this, when the Met had sent reinforcements to help police Brighton during the Labour Party Conference a couple of years ago. Through complete blundering arrogance, Pewe, then a Detective Inspector, had arrested two informants Roy had carefully cultivated over many years and then flatly refused to drop the charges. And to Roy’s anger, when he had taken it to the top, Alison Vosper had sided with Pewe.

Quite what the hell she saw in the man he did not know, unless, as he sometimes darkly suspected, they were having an affair – however improbable that might be. The ACC’s haste in bringing Pewe down from the Met and promoting him, effectively splitting Grace’s duties – when in reality he was quite capable of handling everything on his own – smacked of some hidden agenda.

Normally irritatingly chatty, Glenn Branson had not said a word since leaving the CID headquarters at Sussex House. Maybe he really was hacked off because he was being dragged away from his Friday night with the family. Maybe it was because Roy hadn’t offered to let him drive. Then suddenly the Detective Sergeant broke his silence.

‘Ever see that movie In the Heat of the Night?’ he asked.

‘I don’t think so,’ Grace said. ‘No. Why?’

‘It was about a racist cop in the Deep South.’

‘And?’

Branson shrugged.

‘I’m being racist?’

‘You could have ruined someone else’s weekend. Why mine?’

‘Because I always target black men.’

‘That’s what Ari thinks.’

‘You can’t be serious?’

A couple of months ago, Roy had taken Glenn in as a lodger when his wife had thrown him out. After a few days of living at close quarters, it had nearly been the end of a beautiful friendship. Now Glenn was back with his wife.

‘I am serious.’

‘I think Ari has a problem.’

‘The opening shot on the bridge is famous. It’s one of the longest tracking shots in cinema history,’ Glenn said.

‘Great. I’ll watch it some time. Listen, matey, Ari has to get real.’

Glenn offered him a piece of gum. Grace accepted and chewed, perked up by the instant hit of peppermint.

Then Glenn said, ‘Did you really need to drag me out here tonight? You could have got someone else.’

They passed a street corner and Grace saw a shabby man in a shell suit talking to a youth in a hoodie. To his trained eye, they looked furtive. A local drug dealer serving up.

‘I thought things were better between you and Ari.’

‘So did I. I bought her the fucking horse she wanted. Now it turns out it was the wrong kind of horse.’

Finally, through the clunking wiper blades, Grace could see a cluster of digging machines, a police car, blue and white crime-scene tape across the entrance to a construction site, and a very drenched, unhappy-looking constable in a yellow high-visibility jacket, holding a clipboard wrapped in a plastic bag. The sight pleased Grace: at least today’s uniformed police were getting the hang of what needed to be done to preserve crime scenes.

He pulled over, parking just in front of the police car, and turned to Glenn. ‘You’ve got your inspector’s promotion boards coming up soon, haven’t you?’

‘Yeah.’ The DS shrugged.

‘This could be just the type of inquiry that will give you plenty to talk about during your interview. The interest factor.’

‘Tell Ari that.’

Grace put an arm around his friend’s shoulder. He loved this guy, who was one of the brightest detectives he had ever encountered. Glenn had all the qualities to take him a long way in the police force, but at a price. And that price was something that many couldn’t accept. The insane hours destroyed too many marriages. Mostly, those who survived best were married to other police officers. Or to nurses, or others in professions where antisocial hours were par for the course.

‘I chose you today because you are the best man to have beside me. But I’m not forcing you. You can come with me or you go home. It’s up to you.’

‘Yeah, old-timer, I go home and then what? Tomorrow I’m back in uniform, busting gays for indecent exposure down on Duke’s Mound. Have I got it right?’

‘More or less.’

Grace got out of the car. Branson followed.

Ducking against the rain and howling wind, they changed into their white oversuits and wellington boots, then, looking like a couple of sperm, walked up to the scene guard constable and signed themselves in.

‘You’re going to need torches,’ the constable said.

Grace clicked his torch on, then off. Branson did the same. A second constable, also wearing a bright yellow jacket, led the way in the falling light. They squelched through sticky mud that was rutted with the tyre tread patterns of heavy plant, making their way across the vast site.

They passed a tall crane, a silent JCB digger and stacks of building materials battened down under flapping sheets of polythene. The crumbling Victorian red-brick wall, fronting the foundations of Brighton Station’s car park, rose steeply in front of them. Beyond the darkness, they could see the orange glow of the city lights around them. A loose piece of hoarding clattered and somewhere two pieces of metal were clanging together.

Grace was eyeing the ground. Foundation pilings were being sunk. Heavy diggers would have been criss-crossing this area for months. Any evidence would have to be found inside the storm drain – anything outside would have long gone.

The constable stopped and pointed down into an excavated gully twenty feet below them. Grace stared at what looked like a partially buried prehistoric serpent with a jagged hole gouged out of its back. The mosaic of bricks, so old they were almost colourless, formed part of a semi-submerged tunnel just rising above the surface of the mud in places.

The storm drain from the old Brighton to Kemp Town railway line.

‘Nobody knew it was there,’ the constable said. ‘The JCB fractured it earlier today.’

Roy Grace held back for a moment, trying to overcome his fear of heights, even for this relatively small distance. Then he took a deep breath and scrambled down the steep, slippery slope, exhaling sharply with relief when he reached the bottom upright and intact. And suddenly the serpent’s body looked a whole lot bigger, and more exposed, than it had seemed from above. The rounded shape curved above him, nearly seven feet high, he guessed. The hole in the middle looked as dark as a cave.