The Dionysius’s skipper, Botild Havman, tapped at the picture’s edge. ‘We’re here. We’ll go around it clockwise, a kilometre out.’

‘Won’t that be too far to see anything?’

‘We’ll see enough. And we’ll be clear of most of the bergy bits and growlers.’

Bekker hid his amusement at hearing the terms for smaller ice fragments pronounced in a strong Swedish accent, and went to the windows. The iceberg filled his view, its various strata standing out clearly. The deepest submerged parts were at least a million years old, prehistoric snow compacted into ultra-dense blue ice. D43’s visible bulk was only about a tenth that age, but still ancient. If the plan worked, the residents of Cape Town could be drinking water from ice older than the whole of human civilisation.

Havman issued orders, then brought the Dionysius on a course paralleling the iceberg’s western flank. Bekker watched the great mass slide past. This close, second thoughts rose about the whole project. Would even a couple of repurposed supertankers, the only vessels theoretically powerful enough to tow such a colossal object, be enough?

He considered calling Imka over the satellite video link to voice his doubts, but held off. They had already spoken an hour ago, when the iceberg was first sighted, and the bandwidth was not cheap. Better to wait until he had something specific to report.

The ship continued around the berg. In places, surface snow had been washed away to leave a surreal landscape of glassy ice. D43 had partially rolled as it tore free of the ice cap, exposing strata of cyan and turquoise and deep blue. No photograph could have prepared him for the sheer beauty of the sight. Maybe Imka would regret staying in the warmth after all . . .

His entrancement was disturbed by a discussion between Havman and a crewman. ‘What is it?’ asked the South African.

‘Something odd on the radar,’ the captain replied. ‘Inside the ice.’

Bekker came to see. On the screen, the iceberg showed up as a ragged, fuzzy line to the right of the central dot marking the Dionysius’s position. The ice’s varying density accounted for the radar return’s diffuse appearance – but within it was a sharply defined shape. ‘What’s that?’

‘Don’t know,’ said Havman. ‘It’s solid, though. Rock – or metal.’

‘How could it be metal?’

‘Meteor, perhaps. Or a ship or plane.’

‘That deep in the ice?’ Bekker looked back at the swathes of blue – the product of time, far older than the couple of centuries since humans started to build their ships from metal rather than wood. But the shape on the radar screen seemed too symmetrical to be a mere rock, even one that had fallen from space. So what could it be? He let out a brief, involuntary laugh.

‘What?’ asked Havman.

‘I just wondered if it was a UFO. A spaceship,’ he clarified. ‘But that’s ridiculous. Isn’t it?’