Accident and emergency nurse Kate Wilson has compassion and kindness running through her veins. Her dedication to helping others is the reason she first studied medicine, started campaigning for a better world… and possibly the reason she was mercilessly targeted in a heartless covert mission by undercover police officer Mark Kennedy.

For eight years Kate, known as Katja, shared a life with Mark. They were in an intense relationship for 14 months but after that ended, they remained as close friends for a further five years. They lived together, travelled together, campaigned side by side, sent each other love poems and shared their innermost secrets – or at least Kate did.

Mark had a dark secret he kept to himself. While she was discovering political activism in the late 90s, he was being briefed to infiltrate people just like her as a rising star in the police force.

“The police used me and other women like me in the most despicable way. Under the guise of gathering information they lured us into sexual relationships,” says Kate, 46, who has written a book, Disclosure: Unravelling the Spycops Files, about her devastating experience.

“The police knew what was going on, they had to and they put me and others like me in danger. They claim these officers are vetted but I’ve found out Kennedy failed the psychological test for undercover work but passed it on the second attempt – I’m not quite sure how that works.”

But it did and Kennedy was approved to embark on an undercover operation spanning seven years. In 2003 their two worlds collided when they both attended a meeting at the SUMAC centre in Nottingham, a place where activists of all kinds would come together, advertise events and recruit volunteers. Kate, then 25, knew most of the people there but one day, a new guy sat down next to her who was chatty and engaging.

“We hit it off instantly,” she recalls of the moment she met Mark Kennedy, or his undercover alias, Mark Stone. “I made a joke about the coaches they were booking to take us on a protest being full of socialists selling newspapers. He recognised my accent and revealed he was from London too. We spent the rest of the night whispering like naughty kids at the back of the class.”

Just a couple of days later they caught up again at a house party and spent the night deep in conversation about where they lived and what music they liked. Later, they watched the sun rise together. When Kate revealed she was going to have to hitch hike back to London, Kennedy made an offer of a lift too good to refuse.

Before long they were good friends. “He was a cool guy, he told me he had passed a climbing test which meant he could scale buildings,” she says. “He was one of the few who could drive and had a car so could give me and my friends lifts around the country and he always seemed to be able to find the money we needed to go ahead with protests and campaigns.

Kate’s passion for campaigning began young. As a toddler she attended marches with her parents calling for nuclear disarmament. And she made national news at the tender age of eight campaigning against sexism in under-11s football – yet no one could have guessed the plucky youngster would be back in the news decades later exposing one of the biggest police scandals in modern times.

As a teenager in the 90s during the poll tax riots, she found her heart in raising awareness of social injustices, all of which would be boiled down to one sentence from Kennedy to his handler after their first meeting: “Katja is a white female. She has anarchist connections.” Her fate was sealed.

Kate had no idea about the web being spun around her and how her beliefs would be enough to put her front and centre of an investigation so intense it would see a team of Metropolitan Police officers spy on her, her family and inner circle of friends. Every detail of her life was recorded, from the mundane to the intrusively intimate.

When Kennedy began pursuing Kate romantically, she soon fell under his spell, attracted to his boyish charm and the things they had in common – or so she thought. They quickly moved in together in a houseshare with some of Kate’s other friends who Mark was already living with.

But what she didn’t know was that there were three people in the relationship, probably more, from the start: Kate, Kennedy and EN31, the UCO’s (undercover cop) handler. Unbeknown to Kate, every detail of their relationship was recorded and filed away for police records, from family trips to Ikea to garden parties.

“Mark was on very friendly terms with my parents – they thought he was great,” she recalls. “He came along to many family gatherings but one that still plays on my mind is my nan’s 90th birthday. She sat there chatting with him on the sofa, helping with the food and drink. She died not knowing that her granddaughter’s boyfriend was a fake, someone pretending to be someone else. It’s so degrading. In a way I am glad she never found out the truth but it still makes me angry, he tricked her too.”

Kate later learned her grandmother’s death was one of many personal incidents Mark shared with police in the logs they eventually gave her in full. “The police have a word for it – collateral intrusion,” she explains. “It’s how they [undercover police officers] justify spending hours forging human relationships, sharing a Sunday roast, sanding down an old dresser with my parents, attending family funerals… it’s what we would call it bonding.”

Discovering a partner has lied is one thing but learning they had never truly existed and were only following orders was the awful position Kate found herself in late 2010 when an old friend called to tell her Kennedy had been a police officer all along and they had proof.

After Kate ended their relationship to go and study medicine in Barcelona, he started a relationship with her friend Lisa (not her real name) that lasted for six years with Kate’s blessing. He and Lisa had been to an animal rights meeting in Italy and in the glove compartment of his car she came across an expired passport stating he had a dependent and a phone with messages from his two children and wife – who knew nothing of his secret life other than that he was an undercover police officer – that revealed his vast catalogue of lies.

Kate didn’t learn the truth herself until looking at her phone one afternoon and seeing nine missed calls. “I rang back and an old friend delivered the news – he didn’t want me to find out on the internet,” she recalls. “My first thought was for all the people I had introduced him to and then the shattering truth that my whole friendship and relationship had been a pack of lies. My memories, feelings, experiences just all came crashing down – had nothing been real?”

She returned to London to track Mark’s deception through mutual friends. Several weeks later, she resumed her medical degree in Spain. But, she began to spiral as she struggled to understand the deception and after failing to make the grades she converted to a nursing degree to salvage what was left of her future.

Then almost a year to the day after Kate discovered Mark’s deception, Lisa called her to say she was going to sue the police and asked her whether she would be part of the case.

“I hadn’t slept through the night for a year. I would wake before dawn, paralysed by the mass of questions boiling in my mind,” says Kate of that tumultuous period. “Mornings started with fear. My studies had floundered until it was impossible to catch up and I lost my place at university.

“Lisa’s proposal was an opportunity to do something. Although I didn’t feel I had even begun to understand what had happened, we managed to file a human rights claim 24 hours ahead of the nearing 12 month deadline that would have snatched away the chance forever.”

Eight women brought cases against the police in all but only Kate was able to pursue her human rights claim to the bitter end as she had lost her potentially lucrative career in medicine because of their actions. It took 15 years of legal wrangling for Kate to win a landmark trial against the police for breaching her human rights.

She received a £230,000 pay out in January 2022. It also meant she is the only one to receive full disclosure in the form of thousands of documents the police held from logs with Kennedy while they were in contact. Their last meeting came only months before the bombshell revelation.

“I never fully understood the levels of deceit and intrusion until I read the documents disclosed to me,” says Kate.

Writing her book has helped her knit together the many threads for the first time. When we meet in a South London park, her publisher with her, she holds the first physical copy in her hands and her face flushes staring at her cover photo which she took years earlier when she had just broken up with Mark. Admitting to feeling “overwhelmed”, it’s the only moment she becomes visibly emotional in her interview – an indication of how guarded she has become.

“Finishing writing this really felt like I'd turned this period of my life into something coherent,” Kate says with obvious relief. “Finding out so much of your own life was a lie really messes up your own sense of biography. I didn’t know what my life story was. It’s in a book and it’s clear in my head, at last.”

Kate has since found out there were at least seven undercover officers operating in the activist groups she associated with over a 12-year period. “Everyone had a back story and already knew someone – no one just turned up out of the blue, it was all so plausible.”

She is resolved to spend the foreseeable future supporting the full scale public inquiry and other women involved in the spy cop scandal. Mark Kennedy is due to appear in court next year to explain his actions. Will Kate be there? “You betcha!” she exclaims, her eyes widening. “I can’t imagine what he will say or even that he will actually turn up. But I’ll be there when he does.”

Disclosure: Unravelling the Spycops Files by Kate Wilson is out now (Weidenfeld & Nicolson, £20)