Judgment of the General Court (First Chamber, Extended Composition) of 28 May 2020.#CK Telecoms UK Investments Ltd v European Commission.#Competition — Concentrations — Wireless telecommunications — Retail market for mobile telecommunication services — Market for wholesale access and call origination on public mobile networks — Acquisition of Telefónica Europe by Hutchison — Decision declaring the concentration incompatible with the internal market — Oligopolistic market — Significant impediment to effective competition — Non-coordinated effects — Burden of proof — Standard of proof — Market shares — Effects of the merger on prices — Quantitative analysis of upward pricing pressure — Close competitors — Important competitive constraint — Important competitive force — Network-sharing agreements — Level of concentration — Herfindahl-Hirschmann Index — Error of law — Error of assessment.#Case T-399/16.