Morning mail: May expels 23 Russian diplomats over poisoning Thursday: UK cuts top-level ties with Moscow after ex-spy poisoning. Plus: Peter Dutton considers allowing gun importers to review firearms changes Theresa May told parliament Russia treated the UK's request to explain how the nerve agent novichok was used in Britain with 'sarcasm, contempt and defiance'. Photograph: HANDOUT/Reuters Eleanor Ainge Roy @EleanorAingeRoy Good morning, this is Eleanor Ainge Roy bringing you the main stories and must-reads on Thursday 15 March. Top stories The British prime minister, Theresa May, is to expel 23 Russian diplomats in response to the attempted murder of Sergei Skripal and his daughter Yulia, the largest diplomatic expulsion by Britain in more than 30 years. The UK will also cut off all top-level ties with Russia, including revoking an invitation to the Russian foreign minister to visit the UK, and not sending ministers or members of the royal family to the football World Cup this summer. New laws to combat spying were also possibilities, May said, adding that Russia had treated a UK request to explain how the military-grade nerve agent novichok was used in the attack with "sarcasm, contempt and defiance". She said: "Their response has demonstrated complete disdain for the gravity of these events." Her government had concluded that the Russian state was responsible for the attempted murder of the Skripals. Russia's ambassador to the UK, Alexander Yakovenko, confirmed that British diplomats would be expelled from Moscow, saying Britain's actions were "absolutely unacceptable". The UK has called for an urgent meeting of the UN security council to update council members on the investigation. EU leaders will also discuss the incident at a summit next week, said the European council president, Donald Tusk. Peter Dutton is considering establishing an advisory body to allow gun importers to review proposed changes to firearm regulations for "appropriateness and intent". Following a meeting with a pro-gun lobbyist in February, the home affairs minister is weighing up whether to establish a so-called "firearms advisory council", which the gun lobby says would give it "a seat at the table" to advise the government on firearms policy. Last month Dutton met Robert Nioa, one of Australia's largest gun dealers, to discuss the council. Tens of thousands of school students in America have walked out of their classrooms in unprecedented scenes of mourning and grief, uniting to demand an end to gun violence a month after the Florida high school shooting claimed 17 lives. About 3,000 schools across the country participated in the coordinated riposte, with some students defying the orders of school administrators not to join the protests. At an elementary school in Virginia, children synchronised their watches and a captain in each room led students outside two minutes before the planned start time. Henry Gibbs, 10, said: "Just the sensation that we are going to make a difference makes me feel proud." The Australian government has been warned not to ignore human rights issues as Malcolm Turnbull prepares to welcome leaders from all over south-east Asia. Although Australia is not a formal member of the Asean group of countries, the prime minister is hosting a special summit aimed at boosting trade links to the countries that include Thailand, Indonesia and the Philippines. But with Cambodian strongman Hun Sen and the Thai junta leadership among those attending, Turnbull was warned by human rights groups not to "dance with dictators" at the gathering which starts on Friday. It is arguably Australia's biggest environmental issue. Land clearing threatens our biodiversity, the Great Barrier Reef and our climate commitments. And while each land clearing decision by individual landholders is usually only a small piece of the overall crisis, the power systems that support each decision are the same, writes Michael Slezak in the latest in Our Wide Brown Land series. Familiar faces and familiar patterns reappear again and again in the pro land-clearing battles. Sport José Mourinho is pretty much cooked as a Champions League force, writes Barney Ronay. Manchester United's exit to Sevilla proving their manager's methods, built around solidity and defensive control, no longer work against the best teams in Europe. Jamie Carragher has suspended by Sky until the end of season over a bizarre incident in which the football pundit spat out of his car in the direction of a 14-year-old girl and her father. "We will ensure he gets the help he needs," Sky said in a statement. Thinking time Installation view of Colony : Frontier Wars at the National Gallery of Victoria Photograph: Eugene Hyland The largest collection of colonial artworks will go on display at the National Gallery of Victoria today, at the same time as 200 contemporary works largely produced by Aboriginal and Torres Strait Islander peoples. The twin exhibitions on different floors of the gallery are an attempt to break the traditional packaging of the colonial period in Australian museums, in which the Indigenous response has often been erased. Physicist Stephen Hawking won the world's respect – and gave disabled people like me hope, writes Guardian columnist Frances Ryan. Growing up disabled, Ryan had few role models. But Hawking's brilliant, witty way of navigating the world helped shift the negative stereotypes. "In the vastness of the entire universe, you could say I was one speck and he was another," Ryan writes. "And yet I thought of him as a continual presence in my life, who – perhaps paradoxically, in the light of his illness, not to mention of his work on time – would always be there, somehow." The brain drain from South Australia is a big issue in the state's election this weekend. Columnist Greg Jericho, a proud South Australian, crunches the numbers on the economic weakness that lies behind the problem. The state has lagged behind other parts of Australia since the 90s, he says, and the main reasons are demographics – it has fewer people aged under 50 but more people aged over 50 than the rest of the country. The rapid decline of manufacturing has led to a dependence on agriculture and healthcare, which means more part-time work and flat wage growth. What's he done now? Donald Trump has blamed the plethora of unfilled posts in the US diplomatic corp on Democratic obstruction. "Hundreds of good people, including very important ambassadors and judges, are being blocked and/or slow walked by the Democrats in the Senate. Many important positions in government are unfilled because of this obstruction. Worst in US history!" Trump tweeted. Media roundup The AFR says Labor's tax policy is jeopardising its campaign in Batman ahead of Saturday's byelection, with the Greens capitalising on unrest among older voters. Greens leader Richard Di Natale signalled that if Labor won the federal election, his party would demand changes to the policy to protect those on low incomes. The Herald Sun reports that Derryn Hinch was knocked unconscious after falling from an Uber following an evening out in Melbourne. He will undergo further medical testing today. And the ABC has some interesting analysis from The Conversation on the historical origins of Australian slang, tracing key words and phrases back to Irish and Scots-Gaelic origins. Coming up George Pell's committal hearing resumes in Melbourne after opening to the public yesterday. The NSW government will face questions today about its commitment to rebuilding Sydney's Allianz and ANZ sports stadiums after the plan was withdrawn from Wednesday night's expenditure committee. Supporting the Guardian We'd like to acknowledge our generous supporters who enable us to keep reporting on the critical stories. If you value what we do and would like to help, please make a contribution or become a supporter today. Thank you. Guardian News & Media Limited - a member of Guardian Media Group PLC. Registered Office: Kings Place, 90 York Way, London, N1 9GU. Registered in England No. 908396