‘We could have used this technique of yours sooner.’ Wellington gestured to the map of the battle, which one of his tactical glamourists had sketched in the centre of the tent. ‘The glamourists in the Royal Engineers are restricted to creating the illusion of groves of trees, which is useful at the beginning of an engagement, but not so once forces start moving. In battle, they are largely limited to attempts at breaking the enemy’s attention with flashes of light and blasts of noise. You should have told Mr. Gilman of this Sphère Obscurcie at once. ‘

‘I am not a military man and did not conceive of its potential in war. Once I became aware . . .’ Vincent rubbed his head, showering dirt onto his shoulders. ‘I demonstrated the wrong technique for the Sphère to the French and claimed that it must be worked quickly or it would collapse. I do not think they ever mastered even that. But if they do, their efforts will render them invisible, but sitting in a dark sphere and reliant only on their hearing. The true Sphère is transparent both within and without.’

‘So your wife’s letter stated.’ Wellington beckoned his tactical glamourist forward. ‘Can you teach Major Curry here?’

Vincent assented, and with Major Curry watching, slowly worked the fold necessary to create the glamour. When they vanished, Wellington exclaimed. ‘Good God! Is it as fast as that?’

From her seat, Jane offered a weary smile at his astonishment. ‘Faster, once you have the trick of it.’

Vincent and Major Curry reappeared as her husband untied the fold. His face was paler than she liked, and he shook his head. ‘I fear my strength might be at an end.’

‘I think I have it, sir.’ Major Curry pulled a fold of glamour from the ether. ‘With permission?’

‘Granted.’ Wellington leaned back against a table and watched them.

Major Curry stretched and twisted the glamour, vanishing from view. He cursed. ‘Beg pardon, ma’am.’

‘Not at all, Major.’ Jane smiled at him as he reappeared. ‘Was it black or silver inside?’

‘Silver.’ Red lit his cheeks, but she suspected it was embarrassment at cursing rather than exertion.

‘Then you nearly have it. Do the same fold, but twist it widdershins.’

He glanced at Vincent, who nodded. ‘My wife is an extremely accomplished glamourist.’

The Major attempted it again and disappeared from view. ‘Thank you, ma’am. That did the trick.’

Wellington had him cast the glamour a few more times, watching from within and without. ‘Very good. I want you to train the rest of your team to do this, but tell them that they are under orders not to share the knowledge with anyone. This is a state secret.’

Vincent shifted in his seat, uncomfortably. ‘I beg your pardon, your Grace—’