Mathieu’s thick hair was cropped to a flopping quiff that clung to the forefront of his skull. The rest was shaved down to stubble-blued scalp. He appeared calm and healthy. If anything surprised the primarch about Mathieu, it was his seeming youthfulness. Guilliman had, of course, extensive files on those who had made his shortlist for the role of militant-apostolic, but his natural prejudices assumed the priesthood to fall into a small number of categories: old, mad, dissolute, fanatical or a delightful combination of any of them.

Guilliman made a mental note to adjust his thinking. He was falling into dangerous patterns.

Mathieu was not a bullet-headed rabble rouser, nor a sickly, black-toothed extremist. Nor was he an aged primate, thick with the brocade of office and the dust of inactivity. An air of peaceful placidity radiated from him, and though Guilliman had also encountered this before, Mathieu’s was without the accompanying self-satisfaction that invariably suffused men of faith. His movements suggested a man used to fighting.

A red rope belt cinched his waist. On one side was a simple pouch purse, on the other a battered leather holster for a long-barrelled laspistol. The gun had been taken from him. Felix’s diligence amused Guilliman. The priest posed no threat to him whatsoever.

A servo-skull trailed behind Mathieu at head height, as modest as its owner. A large ‘HV’ was engraved into its forehead, but otherwise it was unadorned. The motor cowling, manipulators and the frame for the single sensor were plain plasteel, and there was no plating of precious metals upon the bone.

Mathieu approached confidently, without outward signs of pious joy at being so close to a son of the Emperor. He did not quake or sing, or burst into tears. He was not afraid. He smiled instead, with an edge of sly humour Guilliman instantly liked. It was a smile that acknowledged the uncomfortableness of the situation, and the un­even power dynamic. It was a smile that said its wearer understood those things, and found them amusing.

The priest stopped before Guilliman on a wide rug. Spreading his arms wide, he bowed low.

‘My lord Roboute Guilliman,’ he said. ‘It is an honour to meet you.’

The priest’s long sleeves brushing the carpet softly.

‘Please, Frater Mathieu, sit.’ Guilliman gestured to a stool built for mortals tucked away under a table. Guilliman had balanced a pile of books on it. Mathieu removed them, and they both sat, Guilliman in his over-sized chair, Mathieu on his stool like a child at a scholum before the master. ‘Do you know why I have called you here?’

Mathieu nodded. ‘I think so.’

‘Then say why.’

Mathieu pursed his lips, raised one knee and clasped his hands around it. ‘It sounds like arrogance when voiced, but to borrow the parlance of your sons, it is the only practical that fits the theoretical. However, I fear I am being tested, and am wary of looking foolish.’