"No, no. I-"

"Suffice it to say," Mayhew interrupted wearily, "that you are safe here from all supernatural threat."

The guard calmed a little. "Safe, you say?"

"England's defences are built on more than the rock of its people."

The lights veered away from the centre of the river towards the Tower of London where it nestled inside the old Roman walls, guarding the eastern approach to the capital. Mayhew couldn't prevent a shiver running up his spine.

"Complete your rounds," he said sharply, overcompensating in case the guard had seen his weakness. "We must ensure that the White Tower remains secure against England's enemies."

"And the prisoner you are charged to guard?"

"I will attend to him." Mayhew pressed a scented handkerchief against his nose to block out the stink of the city's filth caught on the wind. Sometimes it was unbearable. He hated being away from the court where the virtues of life were more apparent, hated the boredom of his task, and at that moment hated that he was caught on the cold summit of the White Tower when he should have been inside by the fire.

He cast his eye around the fortress where pools of darkness were held back by the lanterns strung along the walkways among the wards. The only movement came from the slow circuit of the night watch.

The Tower of London was an unassailable symbol of England. Solid Kentish ragstone formed the bulk of the impregnable White Tower, protected by its own curtain wall and moat, with a further curtain wall and thirteen towers guarding the Inner Ward beyond. Finally, there was the Outer Ward, with another solid wall, five towers, and three bastions. Everything valuable to the nation lay within the walls-the Crown jewels, the treasury, the Royal Mint, the armoury, and England's most dangerous prisoners, including Mayhew's personal charge.