An international maritime labour market study, the thesis focuses on the Dutch naval labour market, analysing wartime Zeeland admiralty crews. The research is based primarily on unique naval pay sources. Analysis of crew compositions has not been made on this scale in the period before. The 1667 Dutch Medway Raid is the starting point, where a few British played a leading role – amongst many others reported on the Dutch side. Pepys and Marvell primarily blamed their joining the enemy on the lure of superior Dutch payment. The thesis asks how many British there were really, how they came to be in Dutch service, and whether this involvement occurred, as indicated, at other times too. Part One is thematic and explores the background mechanisms of the maritime environment in detail, determining causation. First, the two naval recruitment systems are compared and completely reassessed in the light of state intervention in the trade sphere. Two new sets of ‘control’ data – naval wages and foreign shipping – are amongst the incentives and routes determined. British expatriate communities are examined as conduits for the supply of naval labour and civilian support. British personnel are compared and contrasted with other foreigners, against the background of Anglo-Dutch interlinkage and political transition from neutrality through conflict to alliance. Part Two is chronological, covering four major wars in three chapters. Micro-case studies assembled from the scattered record streams enable analysis of the crews of particular officers and ships. Seamen were an occupation that made them a very little known group: the thesis examines the different career types of British personnel of many different ranks, shedding light on their everyday lives. The thesis shows that British personnel were an integral part of Dutch crews throughout the period, even when the two nations were fighting each other. The basic need of subsistence labour for employment took precedence over allegiance to nation/ideology, demonstrating limitations in state power and the continual interdependence forced on the maritime powers through the realities of the labour market.