On 28 May 2020, the General Court of the European Union annulled the European Commission’s prohibition of the merger of the two mobile network operators O2 and Three in the UK in 2016. The Judgment represents a significant blow to the Commission and emphasises the (heightened) burden of proof which the Commission must discharge in order to show so-called non-coordinated effects as a result of which a merger in a non-collusive oligopoly context should be blocked. The Judgment, which the Commission will likely appeal to the European Court of Justice, may have implications not only in the telecommunications sector, but also in the broader context of EU merger policy, illustrating that a four-to-three merger in an oligopolistic market may not necessarily be anticompetitive.