What keeps it up? he wondered. The tunnel had no timber bracing, no metal sleeves to hold the earth at bay. He looked back at the hole into the hydraulic tunnel. Something had excavated this shaft, boring along, then it had run into and pierced the metal sleeve of the hydraulic tunnel. It had then withdrawn, somehow leaving the shaft stable and unshifting.
Aubrey skipped across a shifting shoal of broken roof tile, running his hand along the wall.
He stopped, hissing, and pulled his hand back, nearly slipping on the loose footing.
'Steady.' George put a hand on his back. 'What is it?'
Aubrey wrung his hand and stared at the wall. He passed the lantern to George. 'Shine the lantern up here, please.'
Carefully, Aubrey touched the offending section of the shaft with just his fingertips. It felt different: harder, more like ceramic than earth – even compacted earth.
'Feel this,' he said to Caroline.
She ran her hand along the wall and narrowed her eyes. 'Peculiar. It stops about here. Ordinary earth after that.'
'It's about a yard wide?' Aubrey asked. Caroline nodded.
George hung the pry bar from his belt. He rapped the wall with a knuckle. It made a hard, sharp sound. He reached up as high as he could go, then used the pry bar to extend his reach. Each tap rang back at them.
Finding a narrow piece of timber to balance on, Aubrey crossed to the other side of the shaft. With some reluctance, he touched the wall. Even though he was ready for it, the intense magic made him grit his teeth. 'It's over here, too,' he announced.
He looked up. 'I'll warrant that it goes right overhead, too.'
Caroline and George joined him. Caroline crossed the timber easily, George with a frown and a near-disastrous misstep. 'It's magical,' Aubrey told them. 'Dr Tremaine is boring along underground and stopping the tunnels from collapsing through magic.'
'You knew he'd been here, didn't you?' George said. 'It wasn't just a lucky stab in the dark.'
'I didn't know I knew, if that makes any sense. After the hydraulic station was flooded, a number of things made me think. I'd felt a magical intrusion in the area, just before the flood. But I needed to come down here to see if I was right.'
They pushed on. Four or five yards ahead, Aubrey tapped on the wall with a stick he'd picked up. 'Here it is again. These stabilising rings are like the metal sleeves that were used in building the underground railway. Uncommon sort of magic.' And brilliant. The man's a genius.
'Boring along underground?' George said. 'What for? Some sort of strange hobby? "Excuse me, dear, I'm just off for a bit of a bore. "'
'Here's a question,' Aubrey said. 'What part of the Bank of Albion lies under the ground?'
'The vaults,' Caroline said.
'Exactly.'
'But the Bank of Albion is over there,' George said. 'What's Dr Tremaine doing boring a tunnel over here?'
Aubrey held up a finger. 'Yes. Two good questions. Answers to follow. As soon as we find them.'
'To the bank, then, if we can,' Caroline said, and with that, they were off.
As they went, Aubrey's heart decided to lift its tempo, apparently feeling that the dark, the shadows and the uncertain destination were good enough reasons. His palms began to sweat, in sympathy. Noises alternated, echoing then muffled. Their footfalls and voices made sounds that took on a life of their own, whispering along curves of the shaft.
From all around came tiny groans, clicks, rustlings that seemed to fall silent when they neared, only to start again when they passed.
Side tunnels appeared, opening up at irregular intervals, right and left. Most sloped downward and these showed signs of flood damage. Others curved upward, toward the surface.
All of them had bundles of cable, or chains, or pipes running along the bottom. Sometimes they were buried, sometimes they ran exposed along the bottom of the tunnel. Aubrey grew used to picking across intersections where wires or ropes criss-crossed before disappearing off into the darkness.
Aubrey's sense of the underground world beneath the city grew as they crossed shafts that admitted light from grates high overhead – gas street lights, he assumed. Pipes crossed their paths, emerging from tunnel walls and disappearing again on the other side. These pipes were mostly cast iron, but some were large-bore earthenware pipes and others, on closer inspection, were tarred bundles of wires. They stepped over or crawled under these with extreme caution.
Throbbing. As they pressed on, Aubrey thought he could hear throbbing. No, more than hear it – he felt it through the soles of his boots. It was as if mighty engines were at work around them. But the sound didn't disappear as they moved; it was with them constantly, as much a background noise as one's own breathing.
After half an hour of stumbling and slipping, George stopped and cursed with unaccustomed vehemence. When the lantern light moved and shifted, Aubrey turned to see his friend crouching. 'Resting, George?'
George didn't answer immediately. He used his pry bar to shift some loose earth. 'Vandal,' he growled.
'Who?' Caroline peered at where George was working.
'Dr Tremaine or whoever it was that drove this shaft through here. He's smashed through . . . Here.'
George handed Aubrey a shard of rock. Aubrey turned it over and saw the incised letters. 'What is it?'
'It's marble.' George grunted, then put the pry bar aside and used his arms to scoop earth away, ignoring the disastrous effect this was having on his jacket. 'Latin inscription. Tremaine has shorn off the corner of a Roman ruin.'
A few minutes' work and George had enlarged the hole in the wall enough for Aubrey to see the remains of a pillar.
George leaned back and wiped his brow. 'Roman. From when Albion was part of the empire. Nearly two thousand years.'
'And what's it doing down here?' Aubrey asked.
'Cities are built on the remains of what went before. I hadn't realised how literal this was, until now.' George leaned into the hole with the lantern. 'Mosaics.' He leaned back. 'It's collapsed, in places, but looks pretty solid.'
'You want to explore,' Aubrey said.
'This is exciting stuff,' George said. 'We're the first to see this place for thousands of years. We can't ignore it.'
'It does sound exciting,' Caroline said.
Aubrey had reservations, but shrugged. 'Two out of three. Who am I to argue?'
Climbing down into the ruin was easier than Aubrey expected. Shattered sections of pillars acted as stairs. Some were wobbly, but plenty of handholds made the climbing simple.
Once down, Aubrey could make out what had happened. The ceiling was curved – not a dome, a barrel vault. It had come crashing down, unevenly, but mostly in one solid piece, strong enough to resist being crushed as rubble piled around it and on top. It was a bubble, a gap in the earth that preserved the world of two thousand years ago.
Inside, it was a ruin – mounds of broken stone, vast drapes of spiders' webs, collapsed pillars and broken floor tiles. The lantern threw shadows around that swooped as George swept his arm, surveying the space.