The first British police officer to be convicted of belonging to a neo-Nazi terrorist group has been jailed for more than four years.

Ben Hannam, 22, was found guilty of membership of banned right-wing extremist group National Action (NA) in 2016 until September 2017, following a trial at the Old Bailey.

He had been working as a probationary officer for the Metropolitan Police for nearly two years before he was found on a leaked database of users of extreme right-wing forum Iron March and arrested last year.

Hannam, who pleaded guilty to possessing a prohibited image of a child, was also convicted of lying on his application and vetting forms to join the force and having two terror documents detailing knife combat and making explosive devices.

Judge Anthony Leonard QC sentenced Hannam, who was last week sacked by the Met for gross misconduct, to a total of four years and four months on Friday, with an extra one-year licence period.

“I consider what you did to be very serious and you have harmed public trust in the police by your deceit,” the judge told him.

“I accept your politics… played absolutely no part in your policing and you provided value for the salary you obtained.

“And I do not believe you had any plans to infiltrate yourself into the police force so as to be useful to the far right at any stage. There is absolutely no evidence for that.”

Hannam, wearing beige chinos, a dark blue blazer, white shirt and tie showed no emotion as he was sentenced and taken down to the cells.

Prosecutor Dan Pawson-Pounds said the evidence showed Hannam had “a consistent adherence to neo-Nazi tropes between 2014 and 2019” demonstrated by his internet downloads, social media comments and schoolwork.

The court heard that as early as May 2014, Hannam had expressed intolerant views, writing: “I’m not racist, I just don’t like people who’s (sic) skin is darker than mine!”

His former history teacher said he made “inappropriate” and “offensive” anti-immigration comments during a school Brexit debate.

In March 2016, Hannam signed up to Iron March when he joined the London branch of neo-Nazi group NA.

Hannam, who has autism, told jurors he was “desperate to impress” an older NA organiser who gave him free stickers and badges.

He went on to try to recruit a new member via Iron March and posed in an official photograph on Crosby Beach at the NA national conference in Liverpool in April 2016, jurors were told.

On December 16 2016, NA was proscribed after it glorified the terrorist murder of Labour MP Jo Cox.

But Hannam, of Edmonton, north London, continued to meet high-profile figures in the neo-Nazi group.

Between January and July 2017, he saw them in pubs, at an outdoor boxing event, and when he spray-painted an NA symbol in a storm drain.

On July 19, days after the graffiti trip, which was filmed for a promotional video, Hannam applied to join Scotland Yard.

He fraudulently denied he had ever been a member of the British National Party “or similar organisation”.

Mr Pawson-Pounds said the Met paid Hannam more than £66,000 in salary and benefits and he performed his duties to “an acceptable standard”.

Scotland Yard has said that checks on Hannam’s work revealed no complaints from colleagues or members of the public.

When officers searched his bedroom in March last year, they found Nazi-style posters, notes detailing his membership of NA, as well as NA badges and business cards.

He had stored on a USB stick two documents said to be useful to a terrorist.

Mass murderer Anders Breivik’s manifesto contained guidance on making radiological, chemical and biological weapons, and improvised explosive devices, while the second document detailed how to carry out a fatal knife attack.

Aisla Williamson, defending, said Hannam’s autism made him “vulnerable” to targeting and grooming by NA.

She said he was arrested some three years after his involvement with the group came to an end and that he joined the police, was baptised into the Church of Latter Day Saints and went on to form long-term relationships.

“There is no evidence at all he brought extremist views to his work as a police officer,” she said.

“There is clear evidence of a change of mindset. That is both through his work as a police officer and his involvement in the church.”

Commander Richard Smith, head of the Met’s Counter Terrorism Command, said: “This is a unique case and today’s sentence reflects the gravity of the offences committed by former Pc Hannam.

“Hannam joined and engaged with a right-wing terrorism organisation, whose views are the antithesis of police values.

“He then lied about his past links to this group when applying to become a police officer. His past caught up with him when he was identified as part of a wider, proactive investigation by the Counter Terrorism Command, who moved quickly to arrest him and bring him to justice.”