Rahim Mohammadi — who came from Iran in 2005 and was given indefinite leave to remain in Britain in 2010 — was found guilty at his retrial at the Old Bailey on Thursday, November 29.
Prosecutor John Price QC said Mohammadi, 42, had a "volatile" temper and killed Mrs Adri-Soejoko in February 2017, five months after they clashed at a meeting of the allotment association.
Mohammadi was given the allotment in 2008 by Freedom from Torture, an organisation helping torture victims suffering from post-traumatic stress disorder. It was thought that tending to fruit and vegetables on the allotment would be useful therapy for him.
But the trial heard Mohammadi, who was unemployed, spent much of his time smoking opium and playing video games in his shed on the allotment in Colindale, north west London.
Called Victim a 'Little Witch'
The trial heard Mohammadi called Mrs Adri-Soejoko a "little witch" during a heated allotment association meeting in September 2016.
Detective Chief Inspector Noel McHugh said the victim was a "lovely caring lady" who was a "real pillar of the community."
"Mohammadi was a fellow plot-holder and someone she had known for some years. He was an aggressive, threatening and highly manipulative man and there had been previous issues with him at the allotments. There is no doubt that Lea was very uncomfortable around him. It could best be described that she tolerated him but Lea would ultimately pay with her life," Det. Chief Insp. McHugh said after the verdict.
The trial heard Mrs Adri-Soejoko went missing on February 27 and at 1.40am the following morning relatives reported her missing to the police.
At 2am police officers began searching the allotments and heard Mrs Adri-Soejoko's mobile phone ringing in the darkness.
Eventually they traced it to a locked shed and when they forced entry they found her body inside, with the lawnmower cord still wrapped around her neck.
Mohammadi's DNA Found on Cord Used to Strangle Her
His DNA was found on the lawnmower cord and when he was questioned by detectives he kept changing his story.
Mohammadi — an Iranian Kurd — was eventually charged with the murder but a jury was unable to reach a verdict in February 2018, leading to his retrial.
He will be given a mandatory life sentence when he is sentenced on Friday, November 30.
A Home Office spokesman told Sputnik they could not comment on Mohammadi's case or whether his conviction would affect his immigration status.