But the sheikh believes he can do it. He believes that Allah wants him to do it, and therefore he must and will complete his task. He never contemplates failure. He never shows fear or doubt. And he manages to keeps us all believing, just as he believes. We concentrate on the detail of each step we have to take, and think ‘If this can be made to work, then maybe we can take the next step. If we can get the salmon, alive and well, into the holding tanks in the mountains. If we can keep them reasonably cool in the holding tanks until the rains come. If the rains come and the flows in the wadi are good enough, we can release them through the gates into the wadi. If they turn upstream and run…If, if, if…But, as Fred keeps saying, we have the technology. The rest is up to the salmon.

I try to think of other insane projects where belief has overcome reason and judgement: the Pyramids, Stonehenge, The Great Wall of China-the Millennium Dome, come to that. We are not the first and will not be the last people to defy common sense, logic, nature. Perhaps it is an act of monumental folly. I am sure it is. I am sure people will laugh at us and scorn us for the rest of our lives. You won’t be able to marry me because I will always be the girl who once worked on the Yemen salmon project.

Last night we sat late in our office together, going over equipment inventories, cash flows and project milestones. The sheikh maintains an iron grasp of the detail of his project. If we fail, it will not be because he has forgotten something. While I was clearing papers away and switching off computers he said, ‘Harriet Chetwode-Talbot, I shall always be in your debt. You have worked for me diligently and well.’ He nearly always calls me by my full name. I don’t know why. Anyway, I blushed. He usually gives instructions, rarely praise. ‘You think our project will fail.’

It was not a question. I stammered something in reply, but he brushed aside my words. ‘Think of it in a different way. The same God who created me, created the salmon, and in his wisdom brought us together and gave me the happiest moments of my life. Now I want to repay God and bring the same happiness to my people. Even if only one hundred fish run, if only one fish is ever caught, think what we will have achieved. Some men in my position, with great wealth and the freedom to spend it as they like, have built mosques. Some have built hospitals or schools. I, too, have built hospitals and schools and mosques. What difference does one more mosque or one more hospital make? I can worship God outside my tent on the sands as well as in a mosque. I want to present God with the opportunity to perform a miracle, a miracle that he will perform if he so wills it. Not you, not Dr Alfred, not all the clever engineers and scientists we have employed. You and they have prepared the way, but whatever happens will be God’s will. You will have been present at the delivery of the miracle and you will have been of great assistance to me, but the miracle is God’s alone. When anyone sees a salmon swimming up the waters of the Wadi Aleyn, will they any longer be able to doubt the existence of God? That will be my testament, the shining fish running in the storm waters of a desert land.’

My poor attempt on paper, my inadequate recollections of the sheikh’s words, full of error and omissions, can’t capture the power of the man’s personality. When he speaks like that I can imagine the effect on their listeners that the prophets of the Old Testament must have had. His words, his very thoughts, get inside my head and echo for a long time in my memory, and my dreams.

Now I come to something dark, something I wish had not happened. But I must tell you about it.

When I left the office with the sheikh, his car appeared from somewhere and pulled up beside him and, as he often does, he offered me a lift back to my flat. The chauffeur drops him off first at his house in Eaton Square and then takes me on home, and I usually accept the offer. But tonight I had a headache from looking too long at tiny figures on computer screens, so I said I’d rather walk for a bit, and then jump into a taxi.

I was walking up St James’s Street in the direction of Piccadilly when a tall man in a long navy-blue overcoat fell into step beside me. I hadn’t seen or heard him coming and it gave me one hell of a start. My natural instinct was to turn away from him and cross the street, but before I had a chance to move off, he spoke. ‘Don’t worry,’ he said. ‘I’m a friend of Bob Matthews.’

He stopped then and let me have a good look at him in the street light, and my heart rate slowed down to something like normal. It was so obvious to me that he was a soldier. When my father, and your father and you, and a good many other of one’s friends and relations either are or have been in the forces, it doesn’t take a lot to spot a soldier. He was tall, thin-faced, rather dark-complexioned, with slightly receding black hair and arched black eyebrows over a pair of brown eyes. I don’t know if you will recognise him from that description. He didn’t smile.

‘Who are you? What’s your name?’ I asked him. I think my voice must have been trembling. He had startled me, appearing so suddenly and silently from nowhere.

He didn’t tell me his name. He simply said he was a friend of yours and in the same regiment, and that he had something to tell me. Then he said, and his words chilled me, ‘It’s a lot better for both of us if you don’t know my name. I want to tell you something, but not out here in the street. Do you trust me enough to let me buy you a drink? There’s a place I know nearby.’

I wasn’t so alarmed by then. Instead, I was overwhelmed by the need to know what it was he had to tell me. I knew he would no more harm me than his sister, if he had one. I nodded, still not sure I could trust myself to speak again without a quaver in my voice, and again he scared me by saying we had better not walk together, but that I should follow him after a moment. It made me feel something I never expected to feel, a sense of being watched, a sense of threat in the shadows beyond the light from the street lamps and shop windows. He turned and strode off up the street without waiting for my reply.

He crossed Piccadilly and went down Dover Street. I followed him into a side street where he turned into the doorway of a small pub. It was cramped and noisy and busy inside, but there was a quiet corner where I found your friend sitting at a table waiting for me. Before I could ask him any questions, he suggested we had a glass of wine. I nodded and mumbled something and in a very short time he was back at the table with two large glasses of white wine.

‘I’m not supposed to speak to you,’ he said, without any preliminaries. ‘I’d probably be in a lot of trouble if it was found out I had given information about operational matters to a civilian. So please forget we ever met as soon as I leave here.’

I promised him I would. I looked at him, willing him to get on with it, say whatever dreadful things were as yet unsaid. I knew we would not be sitting there if he could tell me anything good, anything I would want to hear. I thought ‘Oh God, I hope you’re not dead.’ I think he understood, for he reached across the table and patted my hand briefly. Then he told me he was the officer I had spoken to when I rang up the regiment. I didn’t recognise his voice. A cheerful voice had spoken to me; this man was not speaking to me cheerfully.

I told him that everyone kept telling me your whereabouts couldn’t be made known for operational reasons, even though you told me when you went out to Iraq you were just doing a short tour in Basra province.

‘You’re being given the runaround.’

‘What do you mean?’ I said. He paused, then took a slow sip from his glass of wine. He raised his eyebrows and looked at my glass, and I knew he was telling me to have a drink before he spoke again. I drank some wine. It was not very cold or nice but I barely tasted it. The wine went inside me and the alcohol briefly warmed me.