A decade on from the last major disruption of Russian gas supply to Europe, it is looking possible that there will be no transit of Russian gas through Ukraine from the start of next year. The existing transit contract between Gazprom and Naftogaz expires at the end of 2019 and the obstacles in the path of agreeing a replacement are manifold. So are the dangers. Leaving export customers without gas at the height of winter would further damage Russia’s reputation as a reliable supplier – boosting the attractiveness of other supplies, such as LNG from the US. It would also undermine the argument that Europe should use more gas as it seeks to decarbonise energy supply.