‘Not so bad, ratling boy. Isn’t it a marvel what you can do with a scrap of decent grub in your belly? You were right up near the top.’

And Saul felt pride at his climbing.

Below them was a little courtyard hemmed in on all sides by dirty walls and windows. To Saul’s new eyes the robust dirt of the enclosure was almost too vibrant to look at. Every corner teemed with the spreading stains of decay; this weak spot of the city had been convincingly annexed by the forces of filth. A disconcerting line of dolls gently mouldered where they had been placed, their backs to the wall, eyes on the pewter-coloured plug in the corner of the courtyard. A manhole.

King Rat exhaled through his nose triumphantly.

‘Home,’ he hissed. ‘Into the palace.’

He leapt from the top of the wall, landing in a crouch over the manhole, surrounding it. He made no sound as he came to rest on the concrete. His coat drifted down around him, surrounding him like oily puddle. He looked up and waited.

Saul looked down and felt the old fears. He steele himself, swallowed. He willed himself to jump, but his legs had locked into a fearful squat, and he grew exasperated as he readied himself to land beside uncle. He breathed in, once, twice, very deeply, to stood, swung his arms and launched himself at the shape waiting for him.

He saw greys and reds of bricks and concrete lurct around him in slow motion, he moved his body, prepared his landing, as he saw King Rat’s grin approached him at speed; then the world jolted hard, his eyes and teeth juddered in his face, and he was down. His knees pushed all the air out of his stomach, but he smile with exhilaration as he overcame his spasming belly and sucked air into his lungs. He had flown, had I landed ready. He was shedding his humanity like an old snakeskin, scratching it off in great swathes. It was so fast, this assumption of a new form inside.

‘You’re a good boy,’ said King Rat, and busied himself with the metal in the ground.

Saul looked up. He saw figures move behind the windows above, wondered if anyone could see them.

King Rat’s London snarl had assumed a didactic tone. ‘Pay attention, ratling. This here is the entrance to your ceremonial abode. The all of Rome-vill is yours by rights, you’re royalty. But there’s a special palace, the rat’s own hidey-hole, and you bing a waste there through these portholes.’ He indicated the metal cover. ‘Observe.’

King Rat’s fingers scuttled over the iron disc like a virtuoso typist’s, investigating its surface. He turned his head from side to side, cocked it briefly, then suddenly tensed his body and slipped his fingers into infinitesimal gaps between the seal and its shaft. It was like sleight of hand: Saul could not see what had happened, or how the fingers had fit, yet they were there, pulling, in the gaps.

The manhole cover twisted with a yelp of rust. There was a rush of dirty wind as King Rat pulled it free.

Saul stared into the pit. The swirling winds of the courtyard yanked at the rich-smelling wisps of vapour emerging from the hole. The sewer was gorged with darkness; it seemed to overflow, seeping out of the open concrete and obscuring the ground. The organic scent of compost billowed out. Just visible, a ladder driven into the subterranean brick plunged out of sight. Where it was riveted to the wall, metal had oxidized and leached out profusely, making the sewer bleed rust. The sound of a thin flow of water was amplified by the yawning tunnels, making for a bizarre booming trickle.

King Rat looked at Saul. He clenched his hand into a fist, extended a pointing index finger, and his hand described an elaborate twisting path through the air, playfully circling, till it spiralled down and came to rest pointing into the sewer. King Rat stood at the edge of the thin circle. He stepped out over the hole and dropped through the pavement. There was a tiny echoing damp sound.

King Rat’s voice emerged from underground.

‘Down you come.’

Saul squeezed his hips through the hole.

‘Tut a lid on it,’ said King Rat from below, and laughed briefly. Saul fumbled with the metal cover. He was half in, half out of the sewer. He sank under the weight of the metal. He held it above his head and descended. The light disappeared.

Saul shivered in the cold of the sewer. His feet clapped on the metal. He stumbled as his feet hit wetness. He backed away from the ladder and rubbed himself in the darkness. Air gusted and hissed; freezing water flooded his shoes.

‘Where are you?’ he whispered.

‘Watching,’ came King Rat’s voice. It moved around him. ‘Wait. You’ll see. You’ve never tried this, laddie, so hold your horses. The darkmans is nothing to you.’

Saul stood still. His hands were invisible before him.

Shapes moved in front of him. He thought they were real until the corridors themselves began to emerge from the darkness and he realized that those other fleeting, indistinct forms were born in his mind. They were dispelled as Saul began to see.

He saw the muck of the drains. He saw the energy it contained spilling out, a grey light that showed no colours but illuminated the damp tunnels. Before him a study in perspective, the shit-and algae-encrusted walls of the shaft meeting in the distance. Behind him and to his right more tunnels, and everywhere the smell, rot and faeces, and the pungent smell of piss, rat piss. He wrinkled his nose, his hackles rising.

‘No worries,’ said King Rat, a figure saturated in shadows, drenched in them, a mass of darkness. ‘Some cove’s staked a claim and made a mark, but we’re royalty. His territory doesn’t mean fuck to us.’

Saul looked about him. A thin rivulet of dirty water seeped by at his feet. His every movement seemed to set off an explosion of echoes. He stood in a twisting brick cylinder seven feet in diameter. From everywhere came the noises of streaming water and falling stones, and organic sounds of squeaks and scratches, peaking, dying out and being replaced, sounds far away being written over by those nearby, a palimpsest of noise.

‘I want to see you leg it, staying mum as you like,’ said King Rat. He startled Saul. His voice wandered through the tunnels, exploring every corner. ‘I want to see you shift your arse, climb sharpish. I want to see you swim. School is in.’

King Rat turned to face the same direction as Saul. He pointed into the charcoal grey.

‘We’re off that away. And we’re off sharpish. So pull your ringer out and keep up. Ready, my old lad?’

Saul shivered with excitement, the cold irrelevant now, and crouched in a starter’s position.

‘Come on, then,’ he said.

King Rat turned and bolted.

Saul did not feel his legs moving as he followed. The rapid, faint beat of footsteps he heard was his own; King Rat was soundless. Saul could feel his nose twitching and he felt like laughing.

He panted with exhilaration. King Rat was an ill defined blur before him, his coat flapping vaguely in the noisome wind. Tunnels passed by on either side, water spattered him. King Rat disappeared suddenly, cutting sharply left down a smaller tunnel where the water pressure was greater, swirling insistently around Saul’s legs. He pulled his legs up out of the stream.

King Rat turned his head for a second, a flash of pale flesh. He crouched as he ran and pulled to a sudden halt. He waited briefly while Saul caught him up, then ducked into a claustrophobic shaft barely three feet high. Saul did not hesitate, but dove in after him.

Saul’s breath and the sound of his flesh on the brick came bouncing back at him, as loud and intimate as if they existed only in his head. He stumbled, mud smearing his legs, careering along the tube in a messy, effective fashion.

His nose hit wet cloth. King Rat had stopped suddenly.

Saul peered over King Rat’s shoulder.

‘What is it?’ he hissed.