Thomas Mair shot Jo Cox in the head with a sawn-off .22 hunting rifle and then stabbed her 15 times. Photograph: AFP/Getty Images

An extreme rightwing terrorist has been sentenced to prison for the rest of his life for the murder of the Labour MP Jo Cox after a seven-day Old Bailey trial in which he made no effort to defend himself.

Thomas Mair repeatedly shot and stabbed Cox during the EU referendum campaign in June last year. During the attack he was saying “this is for Britain”, “keep Britain independent”, and “Britain first”, the court heard.

The judge said Mair would have to serve a whole life sentence due to the “exceptional seriousness” of the offence.

Mr Justice Wilkie refused a request from Mair for an opportunity to address the
court, saying he had already plenty of chances to explain himself, and
had not done so.

Cox, he told Mair, was not only a “passionate, open-hearted, inclusive and generous” person, but a true patriot. He, on the other hand “affected patriotism” and admired the Nazis.

“It is evident from your internet searches that your inspiration is not love of country, it is an admiration for Nazis and similar anti-democratic white supremacist creeds.”

The crime, he added, had been inspired by “white supremacism and exclusive nationalism, which is associated with Nazism in its modern forms”.

Mair attacked Cox on 16 June this year after she got out of a car in Birstall, a small market town in West Yorkshire that was part of her Batley and Spen constituency. Mair shot her twice in the head and once in the chest with a sawn-off .22 hunting rifle before stabbing her 15 times.

The MP died shortly afterwards in the back of an ambulance, despite emergency surgery. She was 41, and the mother of two children, then aged five and three.

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The moments before and after Thomas Mair murdered Jo Cox – CCTV video

Evidence quickly gathered by the police, including books found at Mair’s home and an examination of his online activities, showed him to be obsessed with the Nazis, notions of white supremacy and apartheid-era South Africa.

Mair was also found guilty of grievous bodily harm of a passer-by who was stabbed when he came to Cox’s aid, possession of a firearm with intent and possession of a dagger. The jury took just over 90 minutes to reach its verdicts.

Mair showed no reaction as the judge denied his request to address the court and was led to the cells. Brendan Cox, the MP’s grieving husband, watched as other family members hugged and wiped away tears.

After the guilty verdict Brendan Cox paid tribute to his wife. He said the family had “no interest in the perpetrator.”

“We only feel pity for him . . . we are here because we want to tell you about Jo. What she was and what she meant to us.”

He said Jo was “interested in everybody, driven not by her ego but her desire to help” and although a fearless and committed campaigner who loved being the MP for her home town, her role as mother of two children always came first. He said the killing was an incompetent political act born out of hate that had instead caused a huge outpouring of love towards Jo and her family.

The Labour leader Jeremy Corbyn said the murder was “an attack on democracy, and has robbed the world of an ambassador of kindness and compassion”.

After the verdicts, Sue Hemming, head of special crime and counter terrorism at the Crown Prosecution Service said: “Mair has offered no explanation for his actions but the prosecution was able to demonstrate that, motivated by hate, his pre-meditated crimes were nothing less than acts of terrorism designed to advance his twisted ideology.”

Following the verdicts, Richard Whittam QC, prosecuting, told the court that Mair had committed a terrorism offence when he murdered Cox, but added that it had not been necessary to prosecute him as a terrorist.

Mobile phone footage shows police detaining Thomas Mair after the murder. Photograph: West Yorkshire police/PA

There were two reasons for this. Mair was charged with murder, which is a crime under common law and not an offence under counter-terrorism legislation; and the jury was only to be asked to decide whether or not Mair had committed the crime of murder. It was not asked to consider his motivation.

Prosecutors acknowledge privately that the febrile atmosphere in which the EU referendum campaign was waged appears certain to have contributed to Mair’s decision to murder his MP, but this played no part in their case. There was no need to refer to the referendum in order to establish his guilt.

The evidence against the 53-year-old unemployed gardener had been overwhelming. He lived in Birstall and witnesses to the attack included people who had known him all his life. The incident was also captured on CCTV, as was his escape.

In his closing speech, the prosecuting counsel, Richard Whittam QC, said Cox had been the victim of a cowardly attack: “The sheer brutality of her murder and the utter cowardice of her murderer bring the two extremities of humanity face to face.”

Mair was charged with Cox’s murder; the grievous bodily harm of Bernard Carter-Kenny, 77, a retired coal miner who was stabbed in the stomach after going to her assistance; possession of the firearm with intent to commit an offence; and possession of a dagger.

Mair listened impassively as Whittam read a statement by Carter-Kenny, who said his life had been turned upside down. “Anxiety and stress were strangers to me,” he wrote. Now he wakes in the night,worrying about what the future might hold.

Flowers and a photograph of Jo Cox left in her memory in Parliament Square, central London, shortly after her murder. Photograph: Ben Stansall/AFP/Getty Images

Mair never denied the offences, but neither did he admit to them. When he appeared at the Old Bailey last month via video link from Belmarsh prison in south-east London, he refused to enter a plea. He made clear that he could see and hear what was happening in court, but when asked how he pleaded, he stared down the camera and said nothing. During the trial he did not offer a defence.

As a consequence, not guilty pleas were entered on his behalf to all four charges, as required by law.

Russell Flint QC, the defence counsel, said Cox had been brutally and callously murdered and her death had had a huge impact on hundreds, perhaps thousands of people, including her husband, parents and young children. He said it was the jury’s duty to decide whether Mair was responsible beyond reasonable doubt. “It is you and you alone who have been charged with the responsibility in determining what are the true verdicts in each of the counts on the indictment.”

Each day during the trial, Mair remained immobile and impassive, staring straight ahead and rarely looking around. He used a notepad, but instead of making notes about the trial, he could be seen to be writing down the names of people in court whom he recognised: a TV journalist, an MP from a neighbouring constituency and a member of Cox’s family.

It was, an observer said, as though he was recording the identities of the people who had come to see him have his day in court.

The sawn-off hunting rifle Thomas Mair used to murder Jo Cox. Photograph: West Yorkshire police/PA