I met Steven Gerrard for the first time on 17 March 2015 at Melwood, Liverpool’s training ground. It was a sunny Tuesday morning and I had just completed three years of work on my latest book, A Man’s World, about Emile Griffith, the gay world champion boxer of the 1960s and ‘70s. There is always a strange ambivalence at the end of years of research and writing about one particular subject – for relief and weariness merge with happiness and uncertainty.

Gerrard was in a far more interesting and poignant place. He had been at Liverpool for nearly twenty-seven years and, having played over 700 times for the first team and after 114 caps for England, he had decided to end his career in this country and move with his family to America where he would join LA Galaxy. Gerrard had also decided that he would commit himself to a new book to follow his first – which had been published in 2006.

I knew he wanted to meet me to discuss whether or not I would write the book but nothing else was obvious. There was no clear indication whether I was just one of a few writers he would meet or even of the kind of book he had in mind. I was also unsure whether I was right for the book, or if the book was right for me. It just helped that I had admired Gerrard as a footballer, and a man, for many years. The chance to meet him was a good enough excuse for me.

He had only returned home in the early hours of that morning, having recovered from weeks of injury to rise from the bench and help Liverpool beat Swansea the previous night. But Gerrard was bright and alert and engaged by the prospect of this book in a way which was hard to resist. He also spoke with stark honesty about some of his disappointments in football – and those moments where he had not quite achieved the success which mattered so much to him. I was struck by the way that, rather than lingering over his many outstanding victories, he talked so openly about his more testing times. He told me a few stories about injuries and heartache which made me sit back and think. These were trenchant accounts of professional football which were so much more vivid and real than snapshot memories of him lifting the Champions League trophy or the FA Cup.

Gerrard said that he had done his homework on me and my past books. He thought we could do something fresh and different. I felt the same and so it was an easy decision to make. We would go for it and both of us felt that a year of work would help us reach somewhere deeper than a conventional sporting biography.

The first big shock took us aback. Any idea that we would be working at breakneck pace to produce a substantial book in just over a year, covering a career of epic proportions and deep intimacy, seemed suddenly ludicrous. The publishers were emphatic. The book had to be written by late June. This was not June 2016. This was June 2015 – just fifteen weeks away.

Deadline day would be Friday 26 June. If we included that very Tuesday it meant that we had exactly 100 days to discuss, research and write a book of around 150,000 words in length. At the same time Steven Gerrard would be engulfed by the most emotional few months of his life as he prepared to say goodbye to the club he would always love, and which had defined him as both a footballer and a person for almost his whole life. He had hugely important games to play in that period for, as he had explained, he was driven by the hope that his final game for Liverpool would on his 35th birthday, on 30 May, in the FA Cup Final.

Gerrard and I looked at each other when we heard the fifteen-week stipulation. Fifteen weeks to write a book? We spoke instead about how we might work together in whatever time we managed to squeeze out of the publishers. I felt we needed to sit down for around fifteen to twenty lengthy interview sessions to discuss his career and his life in detail – while acknowledging that football had to take priority over our meetings.

Gerrard was clear. He would give me all the time I needed and he’d allow me to structure and write the book I saw in my head – while we agreed that, once it was written, he would then go over each line, and every word, in painstaking detail. It was already apparent that, whatever deadline we faced, Gerrard would bring the kind of commitment to a book that characterised him as a footballer. He wanted to do it well; and he cared about how it would be regarded in the months and years to come. This was not going to be a vanity project for him, or an easy pay day. It was a serious proposition.

We shook hands and agreed we would work together. We relaxed. Gerrard pulled a face and laughed when he heard that I was a die-hard Arsenal fan. I felt suddenly sure it would be all right. We would pull it off.

Gerrard also let me know that if I felt the deadline wasn’t realistic then he would tell the publishers and we would all think again. The deal might have to be reworked.

I got home that night and, after telling my family how much I’d liked Gerrard, I railed against the economics of modern publishing. It felt to me as if we might as well be selling shoes – rather than books. Maybe you could design and produce a pair of sensible shoes in fifteen weeks. But write a book? I thought it was impossible.

The following morning I spoke in detail to my agent and to the editor of the proposed book. I trusted and respected them. They were both convinced that the book needed to be published in 2015. It needed to be written in the year that Gerrard said goodbye to his hometown club as its captain, inspiration and most beloved of all Liverpool players. I suddenly knew they were right. I was about to succumb to fifteen weeks of madness.

We were already down to ninety-nine days. I decided that we could probably knock off forty-nine days for interviews, additional research and time away for Gerrard to play for Liverpool while I wrote for The Guardian. If I was lucky I would have fifty clear days of book-writing. I knew that, when the mood took me or a deadline loomed, I could write 3,000 words a day. 150,000 words in fifty days no longer seemed quite so implausible.

I messaged Gerrard to say I thought we could make the brutal 26 June deadline. We agreed to meet a day or two after Liverpool played Manchester United at Anfield that Sunday, 22 March, to begin work.

There would soon be drama. This was a recurring theme, obviously, in the Gerrard story. He was left out of the starting X1 against United, the side that he always loved to beat most, alongside Everton, and consigned to the bench. It had been more understandable against Swansea, the night before we met, for him to be a substitute. That had been his first game back after injury. He had told me that he was pretty sure he would be picked to play against United at Anfield – in his last game against the old enemy.

I wanted Gerrard to rise from the bench and score the winner. I wanted his manager, Brendan Rodgers, to feel he had made a glaring mistake in leaving the great man out of his starting team. I watched the game as closely as if I was having palpitations while following Arsenal.

Liverpool were terrible in the first half. They hardly made a tackle and they were 1-0 down when, at halftime, Gerrard was summoned from the bench. I cheered.

Thirty-eight seconds after the resumption Gerrard was sent off – for stamping on Ander Herrera. It was such an obvious and furious stamp that his red card was inevitable.

I watched Stevie G walk off the pitch and knew that, beyond his personal pain and humiliation, a whole chunk of time had just been taken out of our book. I had interviewed enough great sportsmen over the years to understand that Gerrard would be in no mood to talk.

There was silence for a couple of days and then came the message. We would start working on Thursday 26 March. Ninety-two days were left before deadline. Three months compared to the three or four years I normally needed to write a book. Anxiety and doubt rose up inside me.

But, on that Thursday morning, I began to believe – thanks to Steven Gerrard. Much credit should also go to Paul Joyce, from the Daily Express, who is the football writer that Gerrard trusts most. I had asked Paul, who has known Gerrard for seventeen years, where he thought I should begin the first interview. I knew where I wanted to start but, so soon after The Stamp, I thought it would be cruel to ask Gerrard first about The Slip – the infamous game against Chelsea the previous season when Liverpool’s seemingly unstoppable surge to the league title had faltered in the moment he had slipped and allowed Demba Ba to race away and score.

Paul was unequivocal. “You should start with The Slip,” he advised me. “Stevie knows he has to talk about it – and he will.”

It was invaluable advice. I learnt from that day on that Steven Gerrard would not shy away from confronting his past anguish. He gave me a riveting first interview in which he spoke about how, after the game against Chelsea, he had sat in the back of a car with tears rolling down his face. He had felt so broken that, not wishing his three daughters to see him in such a state, he told his wife Alex that they needed to go away to somewhere quiet and desolate, far from home, so that he could try and bury his pain. He told me how difficult he had found the next few days before, finally, he admitted to himself that he knew the glory of victory – just as he knew the despair of defeat.

Gerrard explained that the dark and the light, the elation and the misery, were familiar. He had lost the Premier League but he had won the Champions League.

He had been through the desolation of Hillsborough and the euphoria of being feted by the Kop. The dark and the light belonged together. It was such a striking statement that one of the book’s key images stood out in my head. It seemed as if the elation and the misery stood together, apart but inseparable, like two posts in an empty goal at Anfield.

We were away then. And in the weeks and months that followed I interviewed Steven Gerrard again and again in diverse locations from Raheem Sterling’s old house to a glass room at Formby golf club, from home to a Liverpool hotel boardroom, from Melwood to Crewe, the night before his very last game, his 710th, for Liverpool. It felt as if we spoke about everything and his insights and memories sustained me in the exhausting weeks and months that followed.

It was hard setting the alarm every morning for 4.30am and, in the last days, 2.30 am, but as I staggered in the dark to my garden shed of an office, I wanted to try and do justice to Gerrard’s honesty and courage, to his loyalty and commitment to Liverpool, to his momentous career. Even then, feeling exhausted and fucked, it felt special to be writing this book.

Towards the very end, and telling myself that I was flying, I even thought that every book should be written amid such fierce intensity. I joked that I might die in the attempt to make the deadline, but I would die happily writing this epic sporting story.

More prosaically, just before lunchtime on Saturday 26 June 2015, I wrote the last word of the book. The word was “Anfield.” I staggered inside, and did a knee-slide across the kitchen floor.

My eldest teenage daughter rolled her eyes, but my wife lent down to give me a kiss and a high-five. It felt special. It felt worth it. I almost wished we could start all over again.