It was only then that I properly registered that he was entirely bald, though from his face I’d guessed he wasn’t more than forty. I blushed, not simply out of embarrassment for my blundering, but because he had already won me over with his life-saving heroics, his composure under pressure, and his courtesy, which I did not think I deserved.

Although I didn’t get to learn the secrets that working for MI5 would have revealed, I soon understood that the hospital had its secrets too, even if they weren’t of national importance.

There was a young woman, a few years younger than me, waiting for a heart transplant. Over coffee, Zac spoke to me about the case in a hushed voice. ‘I shouldn’t tell you, but I trust you.’ Even as my eyes filled with tears to hear that the young woman would almost certainly die, I was imagining how I would write about her in my journal. Zac touched my hand. ‘Don’t be sad,’ he said. There was a tender side to him, despite the swaggering.

When Zac walked through the ward, the eyes of the patients and their families followed him like a flower follows the sun. Zac was a god there, and he knew it. He didn’t bother to hide the fact that he revelled in his power. Zac saw everything. When he saw that my eyes followed him too, he strutted even more.

My grandmother had told me again and again that my long-dead father was a hero, and I did not doubt it. He was a pilot, flying search and rescue for the Royal Air Force, so he saved many lives. It wasn’t rocket science to see why I would be attracted to a charismatic and commanding older man like Zac, who also saved lives. But self-awareness and self-control are not the same thing. The fact that you know you are acting like a cliché doesn’t necessarily stop you from doing it.

I was sitting behind the reception desk. Zac brushed his shoulder against mine as he looked with me at the computer screen. I was working on the notes for an eighteen-year-old male with a heart infection that his mother knew everything about, but a sexually transmitted disease that she knew nothing about. Zac was making sure that both were being taken care of.

‘Have dinner with me tonight. I’ll cook for you.’ He was so full of pent-up energy he seemed ready to vibrate, but he kept himself still, in control. He was like that whatever he said or did, though he displayed an unflappable cool in all of his interactions with patients.

‘Your glasses are steamed up.’ I noticed because I wanted to sneak a glance at his extraordinary eyes. One was violent blue. The other was the real wonder. It was a half circle of cobalt in the top of the iris, and a half circle of brown in the bottom.