‘You want me to write to you? Will I never see you?’

He smiled. ‘You shall come to me when I send for you,’ he said. ‘And if anything happens . . .’

‘What?’

He shrugged. ‘These are exciting times, Mistress Boy. Who knows what might happen? That’s why I need you to tell me what Lady Mary does. Will you do this for me? For love of me, Mistress Boy? To keep me safe?’

I nodded. ‘Yes.’

He put his hand into his jacket and brought out a letter. It was from my father to the duke, promising him the delivery of some manuscripts. ‘Here is a mystery for you,’ Lord Robert said gently. ‘See the first twenty-six letters of the first sentence?’

I scanned them. ‘Yes.’

‘They are to be your alphabet. When you write to me I want you to use these. Where it says “My Lord”, that is your ABC. The M for “my” is your A. The Y is your B. And so on, do you understand? When you have a letter which occurs twice you only use it once. You use the first set for your first letter to me and your second set for your second letter, and so on. I have a copy of the letter and when your message comes to me I can translate it.’

He saw my eyes run down the page. There was only one thing I was looking for and it was how long this system would last. There were enough sentences to translate as many as a dozen letters; he was sending me away for weeks.

‘I have to write in code?’ I asked nervously.

His warm hand covered my cold fingers. ‘Only to prevent gossip,’ he said reassuringly. ‘So that we can write privately to one another.’

‘How long do I have to stay away?’ I whispered.

‘Oh, not for so very long.’

‘Will you reply to me?’

He shook his head. ‘Only if I need to ask you something, and if I do, I will use this almanac also. My first letter will be the first twenty-six characters, my second the next set. Don’t keep my letters to you, burn them as soon as you have read them. And don’t make copies of yours to me.’

I nodded.

‘If anyone finds this letter it is just something you brought from your father to me and forgot.’

‘Yes, sir.’

‘Do you promise to do this exactly as I ask?’

‘Yes,’ I said miserably. ‘When do I have to go?’

‘Within three days,’ the duke said from his place behind the table. ‘There’s a cart going to the Lady Mary with some goods for her. You can ride alongside that. You shall have one of my ponies, girl, and you can keep her at Lady Mary’s house for your return. And if something should happen that you think threatens me or Lord Robert, something very grave indeed, you can ride to warn us at once. Will you do that?’