‘Simple. We cut a deal. I commanded the most powerful army the empire possessed – which wasn’t saying much against the might of the Arab host. But I had sway within the empire at least. The emperor then was a dithering old sheep, put in the purple for the worst of reasons by men ambitious for their own good. I did what I had learned best. I lied. But for the good of the empire. I made a deal with Maslama, and persuaded him to let me have a moment of glory, to be hailed as the new defender of the empire’s lands, and he drew back. In return, I convinced him I would rule for him. For his master. They merely had to come and collect on the debt. He was deceived.’

‘And now he knows.’

‘One imagines. But many things can blind a man to the truth.’ A sudden passion filled his steady gaze. His fist fell hard upon the table. ‘Someone had to take control, damn it! The empire was on its knees! . . . Is on its knees.’ His temper cooled as quickly as it had flared. ‘But now, at least, we may get up. One day.’

‘The city is that strong?’

‘I believe so. But who can predict the hand of history? The Arab is a formidable enemy. The Muslim. . .’ he murmured, trailing to silence.

‘You mean their numbers?’

‘No.’ He turned, frowning, as if it should be obvious. ‘They have no fear,’ he said in a whisper. ‘For them – well, for the best of them – to die in the cause of their god is the highest honour. Not only honour in this life. They die fighting for the promise of extreme reward in the next.’

‘What kind of reward?’

‘Gardens of pleasure, splendid banquets, gold ornaments, silken garments, unending quantities of wine, voluptuous virgins to do their every bidding. . .’ He smiled.

‘Valhöll,’ murmured Erlan, half to himself.

‘What is that?’

‘It is the place of reward for my own people.’ He stared into the empty air, remembering the north. ‘A mighty hall for the chosen who die in battle. Its gates are guarded by wolves. Eagles fly above it. The heroes feast on the boar, Saehrimnir, who comes back to life every time he is butchered. They drink mead from the goat Heiðrunn, whose udders never run dry. The Valkyries – the All-Father’s beautiful maidens – serve them whatever they desire. And all the while the einherjar, the heroes, await the final battle. . .’

For a few moments, Leo said nothing, a subtle smile settled on his lips. ‘A beautiful dream for a warrior.’ He raised his cup to the setting sun where Maslama’s encampment lay. ‘Especially one freezing to death in a foreign land.’ He suddenly leaned forward in a flush of enthusiasm. ‘But can you see – if a man believes this, really believes. . .’ He squeezed his fist before his face. ‘What will he not do? What can he not achieve?’