Many journalists have been murdered in Mexico for trying to expose the narco state, as our special report reveals. Click here to have the Guardian Weekly delivered to your doorThe tortuous journey towards the UK's final departure from the European Union continued this week. After little progress was made over the weekend and on Monday, UK prime minister Boris Johnson headed to Brussels for face-to-face talks with the European Commission president, Ursula von der Leyen, to see what could be done to stop the UK crashing out of the single market and customs union. Could a political intervention draw out a trade deal, or are the UK's demands for â€œsovereigntyâ€ fundamentally at odds with the EU's ideas of a â€œlevel-playing fieldâ€? At the start of this week, only one thing was clear â€“ a deal had to be done very soon if it was to be done at all. Keep up with the latest developments at theguardian.com/politicsOur cover story this week comes from Mexico. The cartel project is a global journalistic collaboration that aims to tell the stories of the many journalists murdered while investigating the narco state. We begin with the story of Regina MartÃnez PÃ©rez, a fearless reporter killed in 2012.