The prosecution described his intent as "chilling".Khalid Ali, 28, who spent five years in Afghanistan detonating over 300 bombs against coalition troops, was found with three knives hidden under his clothes when he was stopped by firearms officers on Parliament Street in April last year.Ali, who grew up in Edmonton in north London and trained as a gas engineer and plumber, had returned to the UK in November 2016. He came under MI5 surveillance a month later when the FBI linked his fingerprints to improvised explosive devices used in Afghanistan.Scotland Yard's head of counterterrorism, Dean Haydon, stated that "due process" led to the authorization to use evidence in the UK was only given a day after Ali planned the attack.An Old Bailey jury convicted him of preparing an act of terrorism in the UK and two counts of possessing an explosive substance with intent. On that same day he bought an 8.5in chef's knife and two 3.5in paring knives, before he travelled to Westminster.After deliberately disposing of his phone in the Thames, officers swooped in to arrest him.Altman told the jury that Ali planned a "deadly terror attack at the very heart of this country's democracy by killing a police officer, a member of the military or even a Parliamentarian". He said: “Chillingly, but for the interception of the defendant by police, he would have carried out yet another murderous terror attack in Westminster.”

The court had heard how Ali’s family in Edmonton, north London, reported him missing in June 2011 after he disappeared without warning. In late October 2016, he appeared at the British consulate in Istanbul, Turkey, claiming to have lost his passport and asking for a temporary travel document in order to get home. Upon his return to Britain in November 2016 he was stopped at Heathrow and his fingerprints were matched to records held by the FBI in the US, who had found the same prints on bomb components seized in Afghanistan. On 22 April last year - one month after the Westminster terror attack - Ali was caught on CCTV walking past the MI6 building at Vauxhall Cross, as well as Westminster Bridge, the Houses of Parliament and Whitehall. Khalid Ali was captured in Berwick Street, London, carrying out reconnaissance in Whitehall during a march on March 18 2017 (Metropolitan Police/PA)

Just after midnight on April 27, his mother called police, saying she had found four knives in her son’s bedroom and she was scared he was going to kill the family. When firearms officers arrested him metres from parliament he had a knife in each of his jacket’s pockets and the other knife in the waistband of his trousers. The moment Khalid Ali was detained in Whitehall on April 27 last year (Metropolitan Police/PA)

In police interview, Ali said he wanted to deliver a “message” to British authorities, but claimed the knives were for protection. We are Mujahideen.”

He admitted involvement in IEDs in Afghanistan, even bragging he detonated more than 300 devices, although he later backtracked. The deputy assistant commissioner Dean Haydon, Scotland Yard’s senior national coordinator for counter-terrorism policing, said “Ali was an incredibly dangerous individual who had returned from a training camp in Afghanistan with a determination to kill police officers, the military or parliamentarians here in the UK.”

Ali, a naturalised British citizen, told his parents he was going to Birmingham on a plumbing job before he disappeared in 2011. Defending the decision not to arrest Ali until April 2017 - when he was armed and within metres of Parliament - Mr Haydon said police and security services were "managing any potential risk he posed and he was arrested at the most appropriate time".
UK citizen Khalid Ali is found guilty at the Old Bailey in London of plotting a terror attack after he was found with knives in the city, and of building and detonating bombs for the Taliban in Afghanistan. He was detained within metres of Parliament, and wished to murder MPs and police officers.