‘No. If I accepted such a peace the people of France would never forgive me. Besides, the Tsar and the King of Prussia would not accept peace on those terms. They want my head. In any case, you are missing the vital point.’

‘Oh?’

‘The allies are divided into two camps: the interests of England and Austria are inimicable to those of Russia and Prussia. That is why they are keen to offer peace. They need France - they need me - to keep the balance of power in Europe. That is their weakness, which I intend to exploit. Don’t you see, Joseph? If I can keep the war going long enough then the alliance against me must break. They will turn on each other and I shall be saved. Then I can make peace with whom I choose. On my terms.’ He smiled coldly. ‘When I have won, history will judge that I am right.’

Joseph shook his head.‘I fear that you are mistaken. You are chancing everything on the hope, the faint hope, that your enemies will set upon each other before they defeat you. It is madness to take such a risk when they offer you peace.’

The burden of the last months of frantic activity weighed heavily upon Napoleon, and the prospect of a bitter dispute with his brother made him feel weary and heavy-hearted. He sighed. ‘I have made my decision. My plans. I will not change them now. I do not deny they may go awry, but I do not feel that destiny has abandoned me yet. So, brother, I will go to war, and you and the others will govern France in my stead. Can I depend upon you?’

Joseph nodded wearily.

‘Then the matter is settled. Save one final duty I ask of you.’

Joseph’s eyes narrowed. ‘What is it?’

‘It is possible that I may be defeated. That I may even be killed on the field of battle. In either event I could not bear the thought of my son being raised as an Austrian prince. I would rather his throat was cut. Do you understand? Under no circumstances is he, or his mother, to be allowed to fall into enemy hands, alive.’

Joseph could not hide the look of revulsion that instinctively rose up in response to the request. ‘I am not a murderer.’

‘It is not murder. It is mercy that I ask of you. If the worst happens, then spare my son, my flesh and blood, the indignity of denying his true identity. I ask you to promise me this. Swear to me that you will give the order. On your honour.’

‘No!’ Joseph raised his hands. ‘Ask anything of me but that.’

Napoleon glared at him for a while, then slumped back into his chair. ‘Very well. I shall have to ask another. But it pains me that you of all people should deny me this comfort before I go to war.’