On 16 June 2016, Jo Cox was murdered while carrying out her constituency duties in the town of Birstall, West Yorkshire. Cox’s death, a politically motivated assassination, came just one week before the Brexit referendum.

Cox was the first sitting MP to be killed since Ian Gow, who was assassinated by the Provisional Irish Republican Army in July 1990, and the first MP to be seriously assaulted since Stephen Timms, who was stabbed in an attempted murder in May 2010.

Cox was first elected to parliament as the Labour MP for Batley and Spen at the 2015 general election. Her murder brought national attention to a line from her maiden speech, which came to define her legacy.

Addressing the commons on 3 June 2015, Cox stated: “We are far more united and have far more in common than that which divides us.”

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At 12:53 pm BST on Thursday, 16 June 2016, Cox was shot and stabbed multiple times by Thomas Mair, a 52-year-old unemployed gardener with long-held white supremacist and neo-Nazi beliefs. During the attack, Mair was heard shouting: “Britain first, this is for Britain.

“Britain will always come first. We are British independence. Make Britain independent.”

Cox, 41, had campaigned for the UK to remain in the European Union. Her murder led to an immediate suspension of campaigning by both sides in the referendum.

In a statement, Cox’s husband, Brendan, said: “Today is the beginning of a new chapter in our lives. More difficult, more painful, less joyful, less full of love. I and Jo’s friends and family are going to work every moment of our lives to love and nurture our kids and to fight against the hate that killed Jo.

“Jo believed in a better world and she fought for it every day of her life with an energy, and a zest for life that would exhaust most people.

“She would have wanted two things above all else to happen now, one that our precious children are bathed in love and two, that we all unite to fight against the hatred that killed her. Hate doesn’t have a creed, race or religion, it is poisonous. Jo would have no regrets about her life, she lived every day of it to the full.”

Parliament was recalled on 20 June 2016 so MPs could pay tribute to Cox.

MPs from across the political spectrum commended Cox for her humanitarian work, particularly on behalf of Syrian refugees, and commitment to compassionate politics.

Jeremy Corbyn, the Labour leader, told the House: “We have lost one of our own, and our society as a whole has lost one of our very best.

“She had spent her life serving and campaigning for other people, whether as a worker for Oxfam or for the anti-slavery charity, the Freedom Fund, as a political activist and as a feminist.”

Corbyn added: “The horrific act that took Jo from us was an attack on democracy, and our whole country has been shocked and saddened by it, but in the days since the country has also learned something of the extraordinary humanity and compassion that drove her political activism and beliefs.”

David Cameron, the prime minister, described Cox as “a humanitarian to her core”.

He stated: “Jo Cox was a voice of compassion, whose irrepressible spirit and boundless energy lit up the lives of all who knew her and saved the lives of many she never ever met.

“Today, we grieve her loss and we hold in our hearts and prayers her husband Brendan, her parents and sister, and her two children, who are just three and five years old.”

Labour MP and mother of the House Harriet Harman recalled meetings where Cox would “not stop kissing” her baby, stating there was “no dividing line between Jo’s maternal heart and her great political heart.”

Stephen Kinnock, who shared an office with Cox, described her murder as a “national tragedy”.

He added: “The fearless Jo Cox never stopped fighting for what is right. She gave voice to the voiceless. She spoke truth to power.

“She exemplified the best values of our party and of our country: compassion, community, solidarity and internationalism.”

Kinnock argued that in the “name of Jo Cox and all that is decent, we must not let this atrocity intimidate our democracy.”

Conservative MP Andrew Mitchell reflected on his time serving alongside Cox on the all-party parliamentary group (APPG) for Syria.

He told the House: “We invited ourselves to tea with the Russian ambassador in his London residence. With clever charm but steely determination, this five-foot bundle of old-fashioned Yorkshire common sense dressed him down for his country’s cruelty and cynicism in Syria.

“I do not believe the Russian ambassador will easily forget that visit.”

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The Jo Cox Foundation was established in 2016 by her friends and family “to build a positive legacy for Jo and to create something positive from the tragedy that was her murder”.

In November 2016, Thomas Mair was found guilty of Cox’s murder and sentenced to life imprisonment.

An October 2016 by-election returned Labour candidate Tracy Brabin, who secured 86% of the vote. The Conservative Party, Liberal Democrats, Green Party, and UKIP did not contest the by-election.

In June 2017, a coat of arms designed with the input of Cox’s children was unveiled in the House of Commons, placed above where Cox usually sat in the chamber.

The motto “More in Common” is displayed below the shield.

In July 2021, Cox’s sister, Kim Leadbeater, was elected as the Labour MP for Batley and Spen.