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ECRQCP

'It's a poor sort of code,' Saladin observed. 'The last few letters are transcribed without change.'

'You're a practical man, I can see that,' Bacon said. 'That's true. But there are easy variants. The simplest is to put the key word at the end of the alphabet, not the beginning, and to proceed backwards.' He scribbled quickly,

'Now all the letters save one have a different symbol.'

'This is all very well,' Joan said, 'but we don't have a key, do we?'

'Oh, but we do,' Bacon said. 'You gave it to me – or rather, to Thomas.'

'I did? What key?'

'It was in the letter you received. From your cousin in Spain. The phrase she was particularly interested in, that appeared to be left incomplete on the scrap of parchment you held.'

'Incendium Dei,' Saladin said, wide-eyed.

Joan stared at Bacon. 'Can it really be as simple as that?'

Bacon grinned. He now had a full hold on their attention, Saladin thought, and he knew it. 'Shall we try it?' He wiped the table clean of chalk with his sleeve, and began to scribble again. The three of them bent over to see. 'We begin with the key,' Bacon said. He wrote,