Orm stared. There was much activity going on in the olive grove. The centre of it seemed to be a kind of machine that nestled among the trees, a long cart that rested on three sets of widely spaced wheels. A large wooden crescent-shape dominated one end, and its upper surface was meshed by ropes and gleaming metal. The whole was obscured by scaffolding, through which a boy clambered, fixing ropes.

The machine was the product of an open-air workshop, Orm saw now. Men and boys moved between furnaces, lathes, piles of timber and tables heaped with gleaming metal components, and scholars came and went between rows of tents among the olive trees.

‘Quite a sight,’ he said, non-committal.

‘It is, isn’t it? What are we building, do you think?’

Orm shrugged. ‘Some kind of wagon?’

‘Come, Orm, stretch your limited imagination. Just look at it. Never mind the scale: tell me what you see.’

The shaft, the bow, the ropes. ‘It looks like an arbalest,’ Orm said. ‘Which the English call a crossbow . . .’ But an arbalest was a gadget small enough for a man to hold in his arms. This machine sprawled across a field, and had a boy actually walking along its back. Orm muttered prayers to the pagan gods of his childhood. ‘By all that’s holy—’

‘Oh, there’s nothing holy about it.’

‘Aethelmaer?’

‘Aethelmaer. Come, let’s ride down.’

Orm remembered Aethelmaer.

In the last days of the reign of King Edward the Confessor, Sihtric had attached himself to the court of Harold, Earl of Wessex, as a priest-confessor - and as a prophet of sorts. He believed he was in the possession of a prophecy already four centuries old, a calendar-like vision called the Menologium of Isolde, whose sole purpose was to ensure an English victory over the Normans in the year of the great comet - the year of Our Lord 1066. Not that it had done much good. Harold, who had refused to take all the prophecy’s advice, had fallen to defeat by the Normans.

But during his career as a court Sibyl, Sihtric had learned of the existence of a rival.

‘Aethelmaer! A fat, crippled monk from Wiltshire,’ he said with some bitterness. ‘Who had also been uttering prophecies about the comet. I’ve since found his very words, among his papers.’ He quoted from memory: ‘“You’ve come, have you, o comet? You’ve come, you source of tears to many mothers. It is long since I saw you; but as I see you now you are much more terrible, for I see you brandishing the downfall of my country . . .”’

‘And you summoned him to Westminster.’

‘Yes. You were there, Orm, you remember.’