This chapter concentrates on the harmonisation of principles relevant to the ascription of in personam jurisdiction. The traditional English common law rules, embracing the inherently flexible concept of forum non conveniens, are contrasted with the universalist rationale of the Brussels Convention, and its hostility to discretionary review, contrary to the certain rules between Contracting States. The ambit of such rules are examined in relation to their determinative effect where the alternative fora are either non-Contracting States, or where the dispute itself has an intra-UK factual matrix. This chapter also reviews tactical strategies that can be applied in the litigational battle for jurisdictional choice of venue, with an evaluation of the appropriateness of foreign jurisdiction clauses, anti-suit injunctions, and negative declarations.