Finally, he spoke up. ‘Well, so this is Asgard,’ he said. ‘What a mess. What a cowboy job. One big puff could blow it down.’ (At this I winked at Heimdall, who bared his golden teeth and growled.)

‘Are you out of your mind?’ said Thor. ‘This is Asgard, the home of the gods. We’ve withstood decades of warfare.’

‘Yes,’ said the man. ‘And it looks it. Wood’s all very well for a temporary settlement, but if you’re looking for permanence, stone’s by far the best way to go. Stone stands in all weather. Stone has a rugged authority. Stone is the future, you mark my words. That’s where the smart money’s going to be.’

Odin looked at the stranger through his blue, unflinching eye. ‘Is this a sales pitch?’

The stranger shrugged. ‘I’d be doing you a favour,’ he said. ‘But I can build you a fortress with walls so high, so massive that nothing – not the Ice Folk, not the Rock Folk, nor even Lord Surt himself – will get through. It’ll be a great investment.’

It sounded like a great idea. I knew how anxious Odin was about safeguarding his position. ‘How soon could you build it? And what’s your price?’

‘Oh, eighteen months, give or take a few. I’m only a one-man outfit.’

‘And your price?’ repeated Odin.

‘It’s high. But I think I’m worth it.’

Odin stood up. From his high throne he looked about twenty feet tall. ‘You’ll have to give me an estimate before you start the work,’ he said. (That’s how you talk to builders.)

The builder grinned. ‘So this is the deal. I’m going to need the goddess Freyja as my wife. And the Sun and the Moon Shields.’

Freyja was the most beautiful of all the goddesses in Asgard. Red-gold hair, skin like cream; she was Desire incarnate. Everybody wanted her – even Odin wasn’t immune – which was why all the gods were outraged at this suggestion (though unsurprisingly, the goddesses seemed willing to negotiate).

As for the Sun and Moon Shields, these had been put in place when Sól and Mani, the sky charioteers, had been assigned their duties. Born from the fires of Chaos itself, bound with runes and glamours, the shields gave their riders protection from the minions of Surt, sent to recover their stolen glam and to return it to Chaos.

To give up Freyja would have been bad enough, but to give up the Sun and the Moon Shields would have been disastrous. Mani, the Moon, who happened to be awake and off duty at the time, went even paler than usual, and Odin smiled regretfully and shook his head.

‘I’m sorry. No deal.’

‘You’ll regret it. One day, Lord Surt will leave his realm to purge the Worlds of you and your kind. You people are going to need stone walls around you, when the time comes.’