Imka chewed unhappily on her lower lip, but turned a dial to increase speed to half astern. The diesel’s revival had also powered some of the electrical systems, a frost-covered light confirming that the command had been received by the machinery in the engine room. The raucous chug increased in tempo – and a grinding noise rose beneath it.

Eddie looked at the exit again, judging how long it would take the ship to reach it against the rate at which the ceiling was descending – and not liking the result. ‘We won’t make it,’ he said. ‘Imka, we’ve got to go faster!’

‘If the engine breaks down, we’ll be stuck in here!’ Imka protested.

‘We’ll be stuck in here anyway!’ She still hesitated – so he reached past her and turned the dial to full.

The engine’s response was immediate, and alarming. A shrill screech came from the lower decks. Eddie forced himself to ignore it and looked ahead again as the Dionysius gained speed. Another rapid calculation. ‘I think we’re going to make it.’ The ship drew closer to the icy tunnel. ‘We’re going to make it—’

A loud bang from below decks shook the bridge – and the survey vessel started to slow.

‘Oh, you had to say it, didn’t you?’ cried Nina, clapping a hand to her forehead.

‘We’re still moving,’ Eddie replied. ‘If we can just keep going, we’ll make it . . .’

‘You did it again!’ She made a plea to the heavens. ‘Fate, if you can hear this: he’s not with me!’

But the Dionysius somehow stayed in motion, trailing sooty smoke as it reached the icy passage. ‘We can do it,’ Eddie whispered, willing it onwards. ‘Just got to get clear of this big lump overhead . . .’

Nina stared at the knobbly protrusion of glassy ice descending inexorably towards them. ‘It’s gonna be close,’ she said. ‘Very, very close.’ It drew ever nearer. ‘Too close!’

Everyone grabbed the nearest solid object for support as the huge mass hit the ship.

With the funnel gone, the tallest part of the Dionysius was the radio mast atop the bridge, which toppled as it was ripped from its mount. Smaller masts for radars and weather sensors followed – then the bridge ceiling tore open, showering its occupants with freezing ice as the obstruction scraped over the superstructure—

Suddenly it was gone, the bridge moving clear, but the obstacle continued towards the foredeck, looking for all the world like a giant tooth about to gnaw on a snack. ‘Hang on!’ Nina cried.

It struck the deck just behind the bow. The whole ship lurched, the stern kicking out of the water – then smashing back down as thick metal plates tore and crumpled like paper. Its upper bow a mangled mess, the Dionysius veered towards the tunnel wall.

Eddie saw the new danger. ‘Imka, we’re going to crash!’