Dominic has extensive experience advising on complex multi-jurisdictional merger clearances before both the European Commission and the UK's Competition and Markets Authority, as well as abuse of dominance and cartel investigations, EU State aid considerations, national security/foreign direct investment reviews and the EU Foreign Subsidy Regulation.

In the UK, Dominic has advised clients on the merger control aspects of a number of high profile transactions including four public interest interventions under the UK’s Enterprise Act 2002. This includes 21st Century Fox on the merger and UK regulatory aspects of its GBP 27.7 billion takeover bid for Sky and the subsequent GBP11.6bn sale of its 39% stake in Sky to Comcast, News Corporation on its proposed acquisition of Sky, Sky on its acquisition of a 17.9% stake in ITV (including before both the Competition Appeal Tribunal (CAT) and the Court of Appeal), and a leading UK retail financial institution on its acquisition by another of the UK’s largest retail financial institutions (including before the CAT). He also advises a number of international clients on highly confidential matters relevant to UK national security considerations and advised one of the UK’s 6 large energy companies on the Competition and Markets Authority’s investigation into GB energy markets, the largest market investigation undertaken in the UK.

At the European level, Dominic has advised on several major cross border transactions including three Phase II clearances before the European Commission. These include advising a global telecommunications services provider on the EU merger control approval of its 50/50 Italian mobile telecoms joint venture with CK Hutchison, the first ‘four-to-three’ mobile telecoms consolidation cleared by the current EU Competition Commissioner Margrethe Vestager, on Hutchison 3G Austria's acquisition of Orange Austria and on Oracle's acquisition of Sun Microsystems.

Dominic is described in the Legal 500 as ‘smart and effective’, a ‘rising star’ and praised for his ‘strong intellect’ and ‘ability to translate legal advice with ease’. WWL, 2022 describes him as having ‘a strong technical grasp of competition law’ whose ‘style is eloquent and persuasive’. Chambers UK 2024 says ‘Dominic Long has a broad competition law practice, assisting clients with issues around subsidy control, behavioural investigations, phase I merger clearance reviews and National Security and Investment Act mandates. He often acts on matters involving the technology and energy sectors.’.