The Beast of Bolsover shook hands with Labour leader Jeremy Corbyn as he took his seat in the House of Commons, before flicking the V-sign towards the backbenches.
Mr Corbyn faced shouts of "Resign!" from Labour MPs as he spoke in the wake of Britain's vote to leave the European Union.
"As political leaders, we have a duty to calm our language and our tone, especially after the shocking events of 10 days ago [Jo Cox's death]," Mr Corbyn said.
"Our country is divided, and the country will thank neither the benches in front of me nor the benches behind for indulging in internal factional manoeuvring at this time."
MPs interrupted him, some talking about him sacking Hilary Benn and others shouting "Resign!".
Prime Minister David Cameron began his speech to the Commons by congratulating the new Labour MP Rosena Allin-Khan, who had been sworn in moments before.
"Let me welcome the new honourable member for Tooting," he said, before joking: "I advise her to keep her mobile phone turned on – she might be in the Shadow Cabinet by the end of the day."
“Lots of vacancies coming up!” someone shouted.
“And I thought I was having a bad day,” Mr Cameron added, to renewed laughter.
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