Cut-off.

The cut-off, the quarter I was diagnosed, was sixty-eight years exactly. I sat on the committee that built the machine that sets the age. I want that stated here, like in the consultation documents, up front.

Steward rations hearts by expected benefit. The benefit is time: the years of good life an organ buys in one chest rather than another, counted, summed and published. Age surfaces with the arithmetic. Each quarter, the model takes the donor forecast and the waiting list and finds the age above which a heart is, on average, better used elsewhere. Each quarter, eligibility is reassessed and candidates above the threshold are automatically suspended. Each quarter, the threshold is published with the full workings attached, forty pages, downloadable, because we believed, and I still believe, that a fatal line you can read is more humane than a lottery you cannot. I have defended it on television. I would defend it again tonight.

What nobody on the committee modelled was the direction of travel. The line was supposed to rise with the donor pool. Instead, lane-assist, the slow abolition of the drunk driver and all cars learning to drive meant that road deaths fell by a fifth in four years, the best news of the decade. As a result, the heart-donor forecast began to fall. The line moved in one direction only, downwards, through the living.

I was diagnosed in January with idiopathic dilated cardiomyopathy. Idiopathic: Latin for nobody's fault. Ejection fraction twenty-three percent and falling on a ruler-straight slope. I was sixty-seven years and eight months old. Eligible, just. I was listed, but the line stood four months above my head like the low ceiling of a slowly flooding room.

In February, I declined Mr Cross. Sixty-nine, a retired structural draughtsman, a year over the threshold, he arrived with the workings printed and annotated in a plastic wallet. He was not there to argue the mathematics. He had come to show me he had read them. I have given the threshold consultation over two hundred times. He listened to all of it with his hands flat on the wallet. At the end, he said the only sentences from that winter I still hear at night.

Do you know what the list does to a man, doctor? I watch the traffic news. Bank holidays. Fog on the M25 motorway. I’ve been a Christian for sixty-nine years but I catch myself hoping for fog.

I told him this feeling was common, that it was no reflection on him. He looked at me as men look at doctors who have understood nothing. He thanked me and took his workings home.

The line moved down to swallow me in July.

My first act was small. I checked my date of birth in the system, character by character, as though a typo might be flooding the room. It was correct. I had entered some of it myself. Then I went looking for the discretionary panel, the route for exceptional circumstances. I found the minute that closed it. Item nine, carried unanimously, my name in the chair. Even the wording of my suspension was familiar. I drafted the template in 2029. I remember arguing for short sentences. Easier on the reader.

I have read the workings. The donor forecast was down again and the list was up. No one decided anything. That is the entire design, that no one decides. I can report from the other side that the design holds. I searched all forty pages for somebody to hate. I found only arithmetic, much of it mine.

The morning after the notice, I performed my last transplant. A heart out of the ice is heavier than anyone expects. I stood in the operating room with someone's next thirty years in my hands. I sewed it into a man of fifty-one. It took. The reason it was his is the line. The line is the reason it will never be there for me. I have stopped waiting.

I still hold the threshold clinics. I have declined eleven patients since my own suspension. I am better at declining them now. They can hear that I believe every word.

Mr Cross had died in March at home. I saw him on the bereavement list, between two other names.

The road casualty figures are published on Fridays. I know this like I know fluid protocols. It has become clinical knowledge, checked without thinking. I read them at my desk with the door shut. Autumn is coming, bringing the early dark. I have caught myself doing the arithmetic, the wet leaves, the half-term traffic, the fog pockets on the M25, which I now know by junction.

I helped build the line. The line is just. I have checked the workings. The workings hold. There is no term in the benefit function for what the threshold does to the people standing on either side of it. There could not be. If the committee sat again tomorrow, I would vote against inventing one. It teaches you what to hope for, free of charge, for life.

For sixty-eight years, I have been a rational man.

I’m hoping for fog.