In 2015, while standing in front of a series of portraits by the American photographer Larry Sultan in the Los Angeles County Museum of Art, Pat Martin suddenly found himself in tears. “For weeks my friends had been telling me, ‘You have to see the Sultan retrospective, you’ll love it,’” he recalls. “And I did, but it triggered me. It was the first time I cried from seeing photographs that weren’t personal to me.”

The portraits in question were of Sultan’s elderly parents, whom he had photographed throughout the 1980s when they were living in a retirement community in Palm Springs. He called the series Pictures from Home and, in a related text, described their deeper motivation: “I realise that beyond the rolls of film and the few good pictures, the demands of my project and my confusion about its meaning, is the wish to take photography literally. To stop time. I want my parents to live for ever.”

Martin, a young Los Angeles-based photographer still struggling to define his own style, found the Sultan exhibition overwhelming but not in the way he had expected. “The portraits were just so beautiful but, alongside that, there was this realisation that, however good I became as a photographer, I could never make those kinds of images. I remember thinking, I don’t know my father and I don’t know if my mother will reach old age. My family album starts with me being born and continues for just a few of my birthdays. Then, it’s just blank. Completely blank. Nothing.”

Gail and Beaux, 2018, one of the two portraits from the series Goldie (Mother) that won Martin the Taylor Wessing prize. Photograph: Pat Martin

Pat Martin was three years old when his father, who made that truncated family album, disappeared from his life, leaving him and his older brother, Drew, with their mother, Gail. So began an anxious, intermittently chaotic upbringing that lasted until he was 17, defined to a great degree by his mother’s struggles with addiction and mental health issues. As a child, he was caught up in the fallout of her troubled life: her dramatically shifting moods; the coming and going of her equally wayward friends; her sudden, unexplained absences, which he later found out were often due to protracted spells in drug rehabilitation clinics. As an adult of 27, he is still addressing the issues of confusion and shame that linger from that uncertain time. “I’m dealing with it in therapy,” he says, “and I don’t plan to stop any time soon.”

Although Martin did not know it at the time, his emotional reaction to Larry Sultan’s Letters From Home was a pivotal moment in a creative journey that culminated in a glittering evening at the National Portrait Gallery, London, earlier this month, when to his surprise he was announced as the winner of the 2019 Taylor Wessing Photographic Portrait prize. Though Martin’s name was unfamiliar to most of the photography insiders present, his portraits, arranged in a line in an adjacent gallery, had been causing a stir all evening. Intimate, raw, direct, they portrayed an elderly woman in often arresting close-up, her dyed auburn hair framing pale, heavy features. In one, she is staring sternly at the camera, clutching a tiny dog, and wearing a T-shirt imprinted with a large dog face.

Pat Martin, winner of the NPG Taylor Wessing Photographic Portrait prize, photographed outside the National Portrait Gallery. Photograph: Amit Lennon/The Observer

The most intimate, though, is the most powerful. In it, her face fills the frame and her mottled skin is a landscape of lived experience, while her averted gaze conveys a brooding preoccupation. It is titled Mom (our last one). It was taken just two months before his mother’s death in January of this year.

“All the photographs submitted to the Taylor Wessing award are judged blind,” says Magda Keaney, senior curator of photographs at the gallery and one of this year’s judges. “With Pat’s work, as with the others, we had no idea of the narrative behind the portraits or even his name or age. All we had were the images and the titles – and Mom (our last one) is, of course, a significant title.”

The judges were struck above all, she says, by the tension in his portraits. “They are tender images, but his gaze is unflinching. He is portraying his mother as she is. His technique is incredibly sophisticated for one so young – the pose, the proximity, the play of the light. The apparent simplicity of his portraits belies his ability.”

A few days after the awards ceremony, I meet Pat Martin at the National Portrait Gallery. Neatly dressed, softly spoken and quietly self-assured, he is, he says, adjusting to the surreal events of the previous days.

Mom (our last one), the other prize-winning portrait from the series Goldie (Mother). Photograph: Pat Martin

“It still feels strange to me that the winning portrait is also my last true portrait of my mother,” he says of Mom (our last one). “The session was almost exactly two months before her death. I didn’t know then that it was going to be the last one, but there was a poignancy to it. Her best friend had just passed on. I wanted to make her feel better, distract her by taking some portraits, but it didn’t work. No response. I put the camera away and I didn’t take any proper portraits for the next month, then her health collapsed.”

Gail had been grappling with respiratory problems for several years. On one occasion, she had called him from a hospital bed in the middle of night after having been admitted for acute breathing problems. Afterwards, he remembers being “suddenly aware that I would not have her in my life much longer.” He began shooting portraits of her soon after she was discharged, slowly moving from observational shots to more considered portraits. That, too, was a pivotal moment. “Before then, I was just another photographer fishing for images on the street and taking portraits of my friends. I wasn’t really feeling anything from it. My mom was the first subject that really made me want to go deeper, though it was a while before I took that on.”

How, though, did she take to the experience? “She was used to me always having a camera in my hand,” he says, “so I don’t think she really thought about it too much. For her, it was more that I was directing my energy towards her.”

So was it a kind of collaboration? He pauses. “Most of the time, yes, but at other times, no. My mom was not an easy subject. She would get bored quickly, like my young nephews do. Or impatient. If she was in a bad mood, it’d be, ‘Are you done?’ or ‘I really don’t want to do this right now.’”

Grandma, 2018, from the ongoing Family-Album series. ‘Gail consoles Jaxson [Pat’s nephew] with a gift in her other hand.’ Photograph: Pat Martin

Martin has edited down hundreds of images of his mother to just 10 portraits which, he says, “meet the standard I have set for myself”. His touchstones are Emmet Gowin and Sally Mann, photographers for whom family is the most intimate and self-revealing subject. Martin’s portraits of his mother are currently part of a bigger, ongoing series, “essentially about my constructed family: my nephews, my brother and his partner, my girlfriend’s family, some older folks that call me their grandson. It’s the family I have chosen for myself.”

Winning the prize, he says, has helped him in his grieving, but I suspect that, like Larry Sultan, he is realising that family portraits of departed loved ones do not so much stop time, as remind us of the cruelty of its inexorable passing. The philosopher, Roland Barthes, confronted with an image of his late mother as a young girl, defined the essential message of the photographic portrait in a single haunting phrase: “That has been.”

I don’t want my mom just to be defined as an addict. She was much more than that

The fact that his mother died alone plays on his thoughts. “I was the last one to see her,” he says, “but I wasn’t there when she passed, and she passed alone. I had left a little while before to go to the dark room. She told me she was going to be OK and not to worry, but…”

Not for the first time, his words trail off into silence.

In their raw power, Martin’s portraits bring to mind the British photographer Richard Billingham’s compellingly brutal, but somehow tender, images of his wildly dysfunctional family as evoked in his now iconic photobook, Ray’s A Laugh. Unlike Billingham, though, Martin did not make photographs from inside the maelstrom of his family drama, but in the relative calm that his mother – and her sons – experienced when she finally overcame her addiction. As such, his portraits have a quietly powerful presence despite their stark honesty.

Their complex charge has much to with his proximity to his subject, emotionally as well as formally, the sense that he is peering closely at his mother in the hope of discovering something revelatory about her troubled life, and in doing so about himself. And yet, she remains oddly elusive, reluctant even under his act of deep looking.

“What I am attempting,” he says, “is definitely a challenge in all sorts of ways. I’m trying to make up for the past that I had and also have a conversation about it.” I wonder if photographs are capable of conveying the intensity of his experience. “I do, too,” he says, “And, I am honestly not sure.”

Going Red, 2016, from the ongoing series Family-Album: ‘Gail dying her hair in my brother’s backyard. My first proper portrait of my mother,’ says Martin. Photograph: Pat Martin

I ask if he has considered using text alongside the images. He tells me that he discovered one of the journals his mother kept while in rehab. “I thought maybe I could use it alongside the photographs, but as soon as I read one page, I put it back in the box. It was clear that, at that point, she did want to live any more.” He pauses again. “That stuff – my mother’s sadness, her addiction – it is so much a part of me still. I don’t know what to do with it. I don’t know if I want to do anything with it.

“It’s a long song,” he says, wearily, of his mother’s struggle with addiction. “I know it went on before my brother, Drew, was born and he is 16 years older than me.” (Martin has made the decision not to reveal the specific drug his mother was addicted to out of respect for her. “It’s complex,” he says, “because I am telling the story to get across the environment I was raised in and how confusing it was, but I don’t want my mom just to be defined as an addict. She was much more than that.”)

I tried to get her to open up, but it was so frustrating. It was like talking to a child, really

Martin grew up in a one-bedroom apartment – “functional, normal, not rundown” – in Mar Vista near Venice Beach in west Los Angeles. His early childhood is shrouded in vague memories, half-truths and hand-me-down stories – and his mother remained unforthcoming to the end. “I tried to get her to open up, but it was so frustrating. It was like talking to a child, really. And, of course, it was painful for her. There were moments when I’d get some answers but mostly it was: ‘I don’t want to live in the past, only the present.’”

His childhood was marked most of all by her absences, which heightened his sense of anxiety. “When I think back on my childhood,” he says, “it’s really just the inconsistency of my mother’s presence that is very evident.”

One of Martin’s earliest memories is of being looked after by some of his mother’s friends and his sense of unease in their presence. Once, aged five, he awoke to find himself alone in the apartment. “I guess my brother had said goodbye to me, but I had been half-asleep. When I woke up and no one was there, I ran outside, scared and crying. The manager of my building found me and brought me in.” A friend of the family, who had been tasked with looking after the five-year-old child, was asleep in another room and remained unaware of the unfolding drama.

A few years later, when his mother relapsed again, Martin’s older brother, exasperated by her broken promises, left the family home for good. Drew and Gail did not communicate for several years, finally reconciling after Drew had children of his own. Throughout all this turmoil, the bond between mother and younger son somehow remained intact and even deepened.

“It’s important to say that my mom wasn’t messed up all the time,” says Martin, ”She was a functioning parent most of the time. She worked as a nurse. She would take me to and from school, make me my lunch. My mother loved me. I was such an extension of her happiness. I knew she was proud that I was her son and I looked so much like her. Plus, because of what we came though – having very little money, living from paycheck to paycheck, food stamps – we had a rapport based on our shared experience.”

Through his childhood and teenage years, his father would call him from time to time, their brief awkward chats only emphasising the distance between them. “There’d be moments when he was kind of there in those phone calls,“ says Martin, looking down and fiddling with his watchstrap. “I knew he was out there somewhere with his wife and his three daughters. Somewhere else.” Speaking about his father, his body language shifts. He becomes fidgety and his sentences become clipped, his voice colder. When he turned 18, they attempted a reunion, but it ended badly. He has not heard from his father since his mother’s death. “I don’t really know why, and that angers me,” he says.

From the series Goldie (Mother), shown as part of his Taylor Wessing series at London’s National Portrait Gallery. Photograph: Pat Martin

For all that, he does not appear to be carrying a lot of anger or bitterness. “I try and tell myself that I’m not angry,” he replies, “but I am. Less so, but it’s still there. My mum was a trigger for my anger for so long, but when I learned that she had been diagnosed as bipolar, that helped explain a lot.”

Likewise the details of his mother’s own fractured childhood which he pieced together from various stories he heard from her and those who knew her: a father who rejected her from birth, who beat her throughout her childhood and disowned her when, aged 19, she gave birth to his older brother, Drew. “My older brother is black,” says Martin, “which is another detail in the mix.”

I realised I did not need to hold this secret any more

All this illumination came late to Martin, emerging fitfully in the years of reconciliation that followed his mother’s final relapse – the point where she reached the place that recovering addicts refer to as rock bottom. That drama began when he was 17 and they were evicted from their apartment for rent arrears. He was subsequently taken in by the family of his best friend and he lived for a time, he says, smiling, “under their staircase like Harry Potter.” He remembers it as a period of “happiness and stability”.

Meanwhile, his mother was free-falling. “For a whole year, we barely saw each other,” he says, “She was going through it again, homeless, living in her car. I only found that out when she called to ask me to pick up the car from the police station. She had gotten arrested. She had the stuff in her car. A couple of days later, she called again to tell me she was going into rehab and gave me all the details.”

From that moment onwards, Pat Martin’s mother seems finally to have found some peace. Three years out of rehab, she was finally reconciled with Drew, and her grandchildren became the focus of a newfound optimism that, though fragile, prevailed until her death. It was Drew, a photographer himself, who encouraged his younger brother to pursue the medium that has helped him make sense of this chaotic family narrative and, in doing so, create the searingly honest portraits that, even without the narrative behind them, have an emotional heft rare in contemporary photography.

Which prompts one last question: why has he chosen to reveal that narrative in such painful detail? Why, in short, did he choose to tell his extraordinary story?

“I chose to tell it for myself.” he replies without hesitation. “Throughout middle school, high school, all my formative years, I hid the facts of my life. I didn’t want anyone to see me as the poor kid with the mother who had a problem. One part of making this work for the past three years was the realisation that my mother would not be around for ever. The other part was the realisation that I did not need to hold this secret any more. When I talk to my brother about it, he puts it very simply: ‘It’s the truth.’”

An exhibition of this year’s Taylor Wessing prize shortlisted works is at the National Portrait Gallery, London, until 16 February