A man cleared of being a terrorist threat by an official anti-radicalisation programme may spend the rest of his life in jail for the assassination of the Conservative MP Sir David Amess. Ali Harbi Ali, 26, stabbed Amess to death on 15 October 2021, fuelled by Islamic State propaganda and having spent at least two years researching which MP to murder. Ali was being radicalised in 2014 at the same time as he was going through the Prevent anti-radicalisation scheme. The Guardian understands that in 2015, while Ali was becoming an adherent of terrorist violence, Prevent concluded he did not pose a significant danger and his case was closed. Amess died barely an hour after the attack at a church in Leigh-on-Sea, Essex, where he had been holding an advice surgery for those from his Southend West constituency. He was the second MP in just over five years to be murdered by a terrorist; in 2016, an extreme rightwing attacker assassinated the Labour MP Jo Cox. Her widow, Brendan Cox, said after Ali’s conviction: “The terrorist will rot in jail and die in ignominy. David’s name will be remembered, especially by the people of Southend whom he served. “Terrorists may cite different ideologies, but what unites them is their desire for infamy, their cowardly attacks on the unarmed and the total failure to advance their cause. All of my thoughts and love are with David’s family today.” Ali, who had once dreamed of being a doctor, was arrested at the scene, having posed as a constituent to gain an appointment. He told police after his arrest that he supported IS and that he had picked Amess, whose constituency surgery details, including location and time were advertised online. Amess, 69, was stabbed 21 times and died in the church before paramedics could get him to hospital. After 18 minutes of deliberation, the jury at the Old Bailey in central London convicted Ali of the murder of Amess and planning other attacks against MPs. He refused to stand as the unanimous verdicts were delivered. Ali, from Kentish Town, north London, took a train to Essex and booked an appointment at the constituency surgery with the sole aim of killing Amess. He lied to Amess’s aides that he had recently moved to Essex. Once in the room with Amess, Ali received a call, said sorry, stood up and pulled a knife from his pocket and began a frenzied knife attack. As Amess lay dying, Ali sent a note from his phone apparently justifying his actions to his WhatsApp contacts and stayed in the church. He did not try to attack anyone else, despite ample time and opportunity. A man who entered the church just after the stabbing saw Ali standing and holding a knife in his right hand, saying: “I want to kill David. I want them all to die.” Ali was on the phone and the witness could hear a female voice saying, “What have you done?” to which Ali replied that he had done it because of Syria and that he wanted to be shot and killed. The man asked Ali why he had done it and he replied: “I wanted to kill David and every MP who voted for bombings in Syria. I wanted to die, be shot and be a hero.” After his arrest Ali told police he had wanted officers to shoot him and had rushed towards them. Instead, once he realised that the first officers on the scene were unarmed, he had heeded their command to drop his knife. He had planned an attack for two years, since May 2019, supposedly angered by western actions in Syria. He had carried out reconnaissance on other MPs, even scouting the home of Michael Gove. He loitered around the Houses of Parliament on several occasions, looking for a chance to strike. Counter-terrorism officials believe he acted alone. Ali had visited the north London constituency office of Mike Freer MP and had been spotted peering in through a window. Searches of his electronic devices showed research on MPs including Dominic Raab; the Labour leader, Sir Keir Starmer; and Ben Wallace. Amess’s killing caused shock and outrage as well as a review of MPs’ security. He was known as a diligent constituency MP with 38 years in parliament. The jury was told the murder was “an attack on democracy”. The issue of whether the level of danger Ali posed was properly assessed may be an issue for the inquest into Amess’s death, expected at a future date. Once Ali was referred to Prevent, he was assessed as being of sufficient concern that he was seen by the Channel programme – reserved for those at greatest risk of radicalisation. Police and security sources have given little detail about his Prevent involvement, which was first revealed by the Guardian. Each year a small proportion of the thousands referred to Prevent are referred on to the Channel programme for more intensive support. DCS Dominic Murphy said after the verdicts: “He spent some time in Prevent and then came out of Prevent and by his own admission carried on his activity in secret over many years, forming his plan and conducting reconnaissance and focusing his efforts on many MPs.” A government-commissioned review of Prevent is expected to be published this month or next. Ali will be sentenced on Wednesday and the crown may ask the court to impose a whole-life tariff, meaning he will never be released. Mr Justice Sweeney said the jury had faced harrowing evidence and excused them from jury duty for a decade, adding: “This is the sort of case none of us will ever forget.”