In a corner of London, close to the busy Edgware Road, there is a secret garden. Tucked away on a residential street, the gate has the words “Colindale Gardens and Allotments Association” messily painted on a white plank tied to the chain-link fencing. Beyond the gate is a broad expanse of grass and earth, of greenhouses, sheds, canes and polytunnels. You can hear the occasional rumble of a train, and in the distance you can see cranes constructing blocks of flats to house the next generation of gardenless Londoners. But the space here is so peaceful, so lush and full of birdsong, that you almost forget where you are.

The Colindale allotments are home to 90 long plots, mostly 20 metres by eight, arranged along two parallel grass avenues. The rules say sheds can be put up only on the end farthest from the path, giving the space the look of a miniature suburban neighbourhood, with plots in front of sheds instead of lawns in front of houses. A plot costs £85 a year. There are currently 60 people on the waiting list.

Rules are important here. The formal ones come from the tenancy agreement all plot holders must sign, which harks back to the Allotment Act 1908: if you break those, you risk forfeiting your plot. Then there are the five “Golden Rules” laid out on its website: number one is, “We respect each other”; number four is, “We treat each other as we would like to be treated”. Everything on the site is overseen by the allotment committee, a seven-strong team of plot holders that meets a few times a year in the grey concrete trading hut near the entrance. Beside it is the only other permanent structure on the site: a shed with a corrugated iron roof where the Mountfield lawnmower, used to maintain the communal pathways, is kept.

This is where Lea Adri-Soejoko, the allotment secretary and treasurer, was found dead at 2am on Tuesday 28 February 2017. She was lying on a wooden pallet, her face covered with a blue coat, still wearing her wellington boots. The starter cord of the lawnmower had been pulled out to its fullest extent and wrapped tightly around her neck. Lea had been strangled by a fellow allotment holder, a man whose plot was only metres from hers, someone she had known for nearly a decade. What might have driven him to murder an 80-year-old woman, in the place she had loved for 20 years?

***

Allotments are precious. There is huge competition for them, with more than 100,000 people on waiting lists in England alone. The high demand means those lucky enough to have one are under pressure not to lose it, to keep it maintained and respect the rules of the site. The benefits of having an allotment are proven: as well as providing owners with fresh home-grown fruit and veg, it helps to keep minds and bodies healthy. A recent study found that people who visit their plots for only half an hour a week have fewer weight problems, and a single session spent on an allotment has been linked to an easing of depressive symptoms and greater self-esteem.

“These allotments are like little green oases,” Adrian Clargo, the Colindale allotments committee chair tells me as we walk together down one of the grassy avenues. “They provide a space for reflection, the opportunity for people, increasingly living in flats, who have no green space to breathe, to meet with other people, to engage with growing something organically.”

Most of the people who have an allotment here are retired and have time to devote to maintaining their spaces. Clargo says only a handful identify as British: the majority are Iranian and Portuguese. “The waiting list operates on a strictly first-come, first-served basis. It’s just the way people have applied,” he explains. “Somebody gets a plot and they let their friends know, so their friends from the same community will all apply at the same time. You get these influxes of people.”

Facebook Twitter Pinterest The hut where the allotments committee meets, and where Lea and her killer had argued. Photograph: Marco Kesseler/The Guardian

The plots are as diverse as the people who hold them. We walk past one that looks like a rubbish dump, strewn with rain-damaged sofas and broken windowpanes. It used to belong to a builder who hoarded things and was asked to leave three years ago, but it can’t be let out again until the management committee works out how to clear it safely. Beside it there is a pristine plot with a stylish shed that has an ambitious glass extension like something out of Grand Designs. We pass another surrounded by what looks like a fence, much higher than the metre and a half allowed in the tenancy agreement; the owner says it isn’t a fence, it’s a support for his beans, but other plot holders have complained.

In this miniature world, minor problems can take on great significance. “We get disputes over what are effectively silly things. Suddenly they become real, difficult things. That’s where the committee comes in,” Clargo tells me. “The allotment is a microcosm of society and the difficulties people have in terms of getting on with each other, understanding each other. It can also be the cauldron of solving some of those problems, of making people understand that we have more things in common than differences.”

People get very passionate about their allotments. “When you come and water three to five times a week, you plant seeds and watch them grow, if somebody comes along and steals your strawberries, that makes you very, very angry,” he says. “It creates an air of mistrust. Sometimes it’s a rumour and sometimes it may be based on a sliver of truth. Then suddenly that creates ripples that can cause all sorts of difficulties.”

Clargo was lucky: when he acquired his plot in 2014 the person across the path was Lea, a Colindale veteran and voluntary secretary on the committee since 2004. “She was our neighbour and she welcomed us in,” he says. “That was fantastic. Although my dad had an allotment, I’d never done it myself. She was able to give me lots of advice.”

Lea liked to grow delicious things: strawberries, leeks, tomatoes, peppers, onions, chicory and tomatoes as well as lavender. “I remember her digging up potatoes – she would share those with us. She had a lovely little wildlife pond at the top of her plot, which has unfortunately been removed by the person who has taken it over.” We stop in front of the plot that used to be Lea’s, now a freshly tilled patch of brown. “She was very organised. She was getting older, so she wasn’t able to look after the plot in the same way that she probably would have when she was younger, but she concentrated on small areas, and those things flourished. She would often sit in a deckchair in her little polytunnel greenhouse.” He pauses for a few moments, his gaze on the space where it once stood. “I’ve seen her asleep in there a couple of times as well.”

Lea had a special combination of softness and strength. “She was a gentle person, very gently spoken. Very kind, very generous with her time. Quirky. Funny,” he says. “She was very, I hesitate to say strong-willed, but she knew her own mind. I’d never seen her ride over people in order to achieve what she wanted, but she just knew what she wanted.” She was physically strong, too. “She looked slight, but I saw her digging and weeding, getting down on her hands and knees to pick things up. She was slower as she got older, but she was still capable of doing what was needed.”

Lea’s family went to look for her. They called her phone. It rang from inside a locked shed

Being on the committee takes time and commitment. Clargo is a primary school teacher and has a young son; he can visit the site only at weekends and during school holidays. But he is now the Colindale allotments’ chair, secretary, treasurer and lettings officer, by default: he took over the roles from Lea and from the former chair, Clive Critchley, who died of cancer last year, and from another committee member who resigned her plot after Lea was killed. Lea lived a stone’s throw from the gate. “That’s one of the things that made her so good as a secretary. She kept the monies and would badger people when they hadn’t paid. Her proximity was key to that. But I think she would come and water every day because she enjoyed doing it, because she enjoyed seeing and talking to people. It was part of her social life, I think. This was her passion.”

Lea was originally from Belgium, and her husband of almost 50 years, who died in 2013, was Indonesian. (Her three children and grandchildren decided they didn’t want to be interviewed for this piece.) While she sometimes told Clargo she was visiting relatives outside London, she didn’t talk about her family much. “She was quite guarded about her private life. I didn’t know about any of her relatives until the tragedy happened.”

A few spaces farther down, on the opposite side of the avenue, we come to an overgrown, sprawling plot, covered with thick grass, apple trees and untamed blackberry bushes. There are vines threaded over a trellis walkway, providing sporadic shade to a couple of chairs and a table that sit outside a ramshackle hut. This plot belongs to Rahim Mohammadi, the man convicted of murdering Lea. He was sentenced to life with a minimum of 19 years last November, following a retrial after the jury failed to reach a verdict the first time he was tried. The space hasn’t been touched or entered since he was charged. “The police have said we can’t let it until they give us the say so,” Clargo tells me. “He still has his possessions in this shed. Even though he’s locked away, they’re still his. We can’t store them for 20 years, and he can’t come and remove them, so we’re in a bind.”

Facebook Twitter Pinterest Forensic officers at the crime scene. Photograph: Jonathan Brady/PA

Mohammadi is a 42-year-old Kurdish-Iranian. He first came to the allotments in 2008 as part of an “allotment therapy” programme run by the charity Freedom From Torture, which provides therapy and rehabilitation services to torture victims. While the precise details of what caused him to leave Iran are unclear, he arrived in the UK with a permanent injury to one eye and scars on his body. Mohammadi sought political asylum in Britain in 2005, and received indefinite leave to remain in 2010. By 2016 he had a plot to himself, and had taken up a role on the committee.

“He enjoyed his growing,” Clargo says. “And he was very helpful.” The committee looks after the maintenance of the grass avenues, and Mohammadi offered to do the mowing. “Rahim knew how the machines worked, and he was here a lot. He did that without any fuss.” But he was intolerant, too. “He didn’t like the way the Portuguese community did things – he was very anti-Portuguese. I would say he was racist in that way, because he would generalise about communities of people rather than individuals,” Clargo says. “But that’s something that we see in society and other allotments as well. It’s not unique to him.”

There are entrenched factions in the Colindale allotments: people from opposite sides of the world with neighbouring plots who don’t always get along. As Clargo puts it, “You’ve got people who’ve got very different ideas about how things should be done, and only a very small path in between you.”

When Clargo took on the role of lettings officer he saw the membership list for the first time, and was surprised to discover that Mohammadi lived in Hackney, east London, well over an hour’s journey from Colindale. “I thought, why on earth are you not registered with an allotment closer to you?”

***

Jochen Encke, a psychotherapist for more than 40 years, has some idea why Mohammadi wanted to stay in Colindale. He spent a decade working with Freedom From Torture, providing therapy to people with post-traumatic stress disorder (PTSD) from around the world. Mohammadi was one of his clients, and he spoke in his defence during both his murder trials. I tracked Encke down, and he eventually agreed to speak to me on the phone.

“There was always a group of people who could not receive psychotherapy,” Encke tells me in his broad German accent. “Sometimes the trauma was so immense, talking about it wouldn’t have helped. That’s what post-traumatic stress disorder is: you’re so wrapped up in your trauma that there’s no space for anything else. Plus, most of the people I worked with didn’t speak a word of English, and psychotherapy is stuck without talking.”

Facebook Twitter Pinterest Lea’s memorial, near the allotments’ entrance. Photograph: Marco Kesseler/The Guardian

Allotment therapy offered people an opportunity to get away from their trauma. “The idea was to explore whether we could open up something with them there. When you are distressed and you walk in nature, you feel better. I tried to take psychotherapy entirely out of it. I said, ‘Let’s not talk about anything, let’s just be together and explore something larger than ourselves.’”

In the 10 years the project was running, more than 100 people came to Colindale for allotment therapy. They were referred to Freedom From Torture by lawyers, doctors and social workers, and came from Iraq, Iran, Sudan and across Africa. “Wherever the crises were at the time,” Encke says. They had all experienced extreme traumas, such as sleep deprivation, being hung upside down for hours, electrocution, being left alone in a dark room for months, or having their fingernails pulled out.

Every Wednesday, they met at the allotment and worked on the five plots the charity rented. They grew potatoes, onions, garlic, and sometimes seeds that were sent from their home countries, and they often cooked what they had grown together on a barbecue. People did whatever they wanted: Encke remembers one client who used his time there to sleep on the warm compost heap.

“It was immensely successful, and it blew my whole idea of psychotherapy. I could see the power of not always going back and analysing,” he tells me. “It was my best day of the week, full of banter, humour, lightness. It was amazing how people who were so traumatised, within months started laughing about themselves and the world. Of course, we had times when we talked about things that happened – there was no doubt about that – but actually they all discovered they were much bigger than the trauma. And nobody could take that away.”

When I ask Encke what Mohammadi was like, he sighs and pauses for a full 10 seconds. “When I first met him he was utterly withdrawn. He couldn’t speak, he couldn’t look at you. He was just a frightened little puppy.” Encke doesn’t know the details of what Mohammadi endured in Iran, beyond that he had been a political dissident, part of a wealthy family, and that his father had also been imprisoned and tortured. “Slowly, he became more alive, more active. I knew him for 10 years, eight years on the allotment, and at the end he was quite self-sufficient. He became a member of the allotment committee, and got back his political self. That was when he got in trouble.”

Facebook Twitter Pinterest Rahim Mohammadi, Lea’s killer. Photograph: Metropolitan Police/PA

The allotment project stopped four years ago; Encke says Freedom From Torture cut it to make savings. He kept in touch with Mohammadi, who organised reunion barbecues on his plot every couple of months. “I could feel that things were shifting. All my work on the allotment was to focus on having less, finding peace by letting yourself go. But once I left, that spirit left; it became another little society where people competed with each other. They wanted a bigger allotment and a bigger greenhouse and Rahim got into that, too. He wanted to be part of the management committee and then he wanted to become a manager, more, more, more. The whole spirit of ‘less’ was gone.”

Encke says he doesn’t know what happened that February day with Lea. He has stayed in touch with Mohammadi since he was charged, and visited him on remand in Belmarsh prison. “Guilty or not, my relationship with him hasn’t changed. But I can imagine that if they had a row and he was threatened with having to leave the allotment, that would have been a lot, because the allotment was everything to him.”

***

On the other side of London, in a tower block next to the Thames in Putney, I meet DCI Noel McHugh, the Metropolitan police detective who led the investigation. His office overlooks the high street, and his desk is littered with used coffee mugs and tubes of Berocca. It is a busy time for detectives in London, with fatal knife attacks at their highest level since records began. “Normally we have young men running around stabbing each other over nothing,” McHugh tells me. “It’s now very rare for a female to be killed outside of domestic abuse. And an elderly lady, too. It makes you think” – his eyes widen – “‘Really?’”

On the evening of 27 February 2017, Lea was meant to attend a meeting of Barnet Allotment Society, but she never arrived. Her daughter, Tess, and granddaughter, Amber, rang her mobile. When there was no answer they tried her house, but found it empty and locked. They searched for her in the streets around Colindale and called the local hospitals before finally reporting her missing at 1.40am. It was only then, accompanied by police officers, that they went to the allotments; the gates were locked but they found a hole in the fence and crawled through. In the darkness, they carried on calling Lea’s phone. Eventually, they heard her ringtone coming from the padlocked mower shed. The police forced the lock, and found Lea’s body next to the mower. There were no signs of a struggle, but Lea had a fractured spine and ribs, and bruising and abrasions on her face – injuries that suggested someone had struck her and rendered her unconscious, before finally strangling her here.

“The family and police saw Lea covered up with a coat over her,” McHugh says. “Our interpretation was that someone who knew her had killed her. Someone who couldn’t face looking at her.”

The allotments were immediately cordoned off so investigations could begin. “Normally we have house-to-house where we knock on every door. Here we had allotment-to-allotment,” says McHugh. At first Mohammadi was a witness, not a suspect. In his initial police interview, he said he had travelled to Colindale on the afternoon of 27 February and picked up a gate key from Lea at her house before going to the allotments; he claimed to have been to her house many times, often doing odd jobs for her. “He painted it as a very close relationship; the family and other allotment owners presented that Lea was very uncomfortable around him. There had been a dispute at a previous meeting where he had shouted at her,” McHugh says. “His perception didn’t hang together. Second or third day in, he started to stand out.”

When I ask him what he thinks the allotments meant to Mohammadi, McHugh takes a deep breath. “It really was his life, that’s the best way to describe it,” he says. “He would know the ins and outs of whatever was going on. Witnesses said he wanted to be involved in everything, he was trying to advance his own position. Lea was established, well-respected, she was everything that he wanted to be and she didn’t have to try hard to get it; it came naturally to her. He wanted status within the allotments. And we had the feeling that he had the ability to snap.”

Mohammadi’s behaviour on the day Lea’s body was found added to the investigating team’s suspicions. “He turns up at the allotments – it’s all taped off, the police are there. He approaches the police cordons and doesn’t ask about what had happened. He doesn’t try to check in with Lea to see how she is, whether she knows what’s gone on, is everyone all right. For me it was just implausible. For someone who was so” – he chooses the word carefully – “obsessed with the allotments, you’d think he would be thinking, what’s this all about?”

Facebook Twitter Pinterest Rahim’s overgrown plot. Photograph: Marco Kesseler/The Guardian

The investigative tools that are normally the cornerstone of any murder investigation weren’t immediately relevant in this case: there was no CCTV on the allotments. Mohammadi’s Oyster travel card placed him in Colindale during the time of the murder, but he readily admitted to being there, and he usually mowed the lawns, so it made sense for his DNA to be all over the mower shed. “He put forward in his defence that he was responsible for maintaining the mower. He gave a great description of how he does that. But his DNA was very low down on the pull cord.” There would be no reason for touching the furthest extent of the pull cord if you were simply using it to start the mower or maintain it.

The locked mower shed padlock became central to the investigation: it required a key to both lock and unlock it. “Whoever killed Lea would have to have locked the padlock and would have needed the key to do it.” Five keys were known to exist: Mohammadi had one, Lea’s copy was found on her body, and the three others were accounted for with other allotment holders who had alibis. Mohammadi was charged with Lea’s murder a week after her body was found.

In court, Mohammadi said he regularly took opium for back pain, and he used it on the site, in common with several other Iranian allotment holders. CCTV footage from the surrounding streets on the day of the murder shows him wandering back and forth around Colindale. He claimed to have spent most of the afternoon watching YouTube videos in his shed, but also that he went to get opium from a dealer, and later visited local shops to buy water and tobacco. But it has been difficult to establish what actually happened between Mohammadi and Lea that day. It was pouring with rain, and no one saw them together.

Perhaps the most important insight comes from the committee meeting that took place four months before the murder, a meeting that became a key part of the evidence in the case against Mohammadi. “It was in here,” Clargo says as he leads me into the trading hut next to the mower shed, a cold, dark space divided in two by shelving racks. On one side there is a narrow table surrounded by seven metal chairs. Clargo explains that six members of the committee were sitting around the table, and Mohammadi was talking loudly about something – Clargo can’t remember what, but during the trial it emerged Mohammadi wanted a Portuguese allotment holder, who kept chickens and rabbits in a shed on his plot, evicted.

This has nothing to do with refugees. It is about the actions of one wicked individual

“Lea just said, ‘Oh Rahim. Shut up.’ And he took real, violent offence at that. He stood up and was pointing at her, gesticulating.” Clargo stands in the space where Mohammadi had stood, pointing down at the empty chair where Lea had been sitting. “‘Don’t tell me to shut up, you fucking bitch!’ he said. He had his keys around his finger. It was very threatening and he didn’t move away. He was quite a tall chap. She stayed sitting down. I wanted to step in, but Lea was sitting between him and me, so I couldn’t.

“I think everybody there felt threatened. Clive took Rahim outside the shed to say that, no matter what anybody says to you, that’s not an acceptable way to respond. All of us said, that cannot happen again – we all spoke to Rahim afterwards individually. It was one of Lea’s throwaway quirky comments, where she was just trying to move the agenda on. Obviously it was a little bit clumsy and he took it to heart and exploded. But he wasn’t an explosive element in every meeting. It was uncharacteristic.”

Lea apologised for telling him to shut up, but Mohammadi remained angry. He wrote several emails complaining about Lea, accusing her of a “conspiracy” to prevent the rest of the committee seeing bank statements. “She does not understand every member has the same rights she has. I don’t understand why she [is] scared to show a bank statement to others!!!’” he wrote in one.

The prosecution argued that Mohammadi’s anger must have exploded once more on the day Lea was killed, this time manifesting in physical violence; that he beat Lea in a rage, and then, realising that his outburst was going to cost him the allotment, he took her into the mower shed and killed her in cold blood. The police suspect he had intended to move Lea’s body and conceal it later, but it was discovered before he could.

When Mohammadi was led from the dock after the verdict was read, he turned to the jury and said, “You will have that on your conscience – sending an innocent man to prison.” It was a comment that made several people from the allotment uncomfortable. I spoke to another Iranian plot holder who didn’t want to be named but said Mohammadi “was not brave enough” to kill anyone. But he could not account for the padlock evidence, and he could not suggest anyone else who might have had any animosity towards Lea.

Facebook Twitter Pinterest The Colindale allotments in London, where Lea Adri-Soejoko was murdered. Photograph: Marco Kesseler/The Guardian

“He’s the only person who could have done this to her. We’ve seen justice done,” McHugh says. “It’s unfortunate Rahim can’t tell us what happened that day. If he could, Lea’s family might be a step closer to moving on.”

***

Clargo is still baffled by what happened. “I’ve seen those qualities of passion and being quick to anger in lots of people. Does that mean they are all potential murderers? It makes you question your judgment.” He sighs. “Rahim is an immigrant who came to this country because he was experiencing violence in his own country. He had a wonky eye and he didn’t speak English very well. So if you were looking to find somebody who would look like an oddball in society, he fits a lot of the criteria. That’s what makes me feel slightly uncomfortable. But that doesn’t mean he didn’t do it.”

Once Mohammadi was convicted, the Mail Online’s headline described him as a “One-eyed Iranian given asylum in Britain”. Lea’s family were appalled by the coverage. Speaking after the verdict, her son, Mark, said, “Some people make a play about the fact he is an immigrant or refugee, but it’s not to do with that. Where they come from has nothing to do with it. We are the children of immigrants. This is about the actions of one wicked individual.”

The shed remains boarded up, the mower still inside, untouched, since being declared a crime scene. Clargo says Lea’s family want to knock it down, and the committee would be happy to see it go. A few paces away, beside a wooden bench, there is now a small patch of garden dedicated to Lea’s memory, with a brass plaque paying tribute to “A Great Servant of the Allotments for Many Years”. The memorial garden is filled with vibrant colours: narcissus, tulips, rhododendrons and red-leaved Acer palmatum ‘Corallinum’. There are tea-light lanterns, a bird bath and a tiny pond. It is a place for attracting life.

The Colindale Safer Neighbourhood team now has a key to the gate so it can patrol here, and the committee is working to install CCTV. That hasn’t been enough to reassure everyone. Six people gave up their allotments in the weeks following Lea’s murder. Clargo himself has decided not to renew his membership and will be stepping down from the committee at the next AGM; he says he feels safe here, but the allotment is taking over his life, and he wants to spend more time with his family. “My plot will go to the next person on the waiting list,” he says. “It will be very well received by somebody.” He is leaving without any idea who will replace him on the committee, in the roles that meant so much to Lea, and to the man who was prepared to kill her for his chance to keep his place.

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