Limited empirical evidence in support of world-city formation has been the ‘dirty little secret’ of the eponymous research area. Since the late 1990s, inspired by Sassen’s account of The Global City, the field focused on advanced producer services (APS) firms as primary actors in world-city formation. While generating robust insights into the shifting geographies of world cities, empirical attention has mostly focused on mapping inter-urban world city networks formed by APS firms. Despite a rich literature on APS clusters, the degree to which specific intra-urban agglomerations and their inter-firm connections shape up has received little systematic attention. Based on a company survey in Brussels (Belgium), our study charts interactions between APS professionals to better understand the geographies, quality and intensity of their encounters. Our findings reveal that the Brussels-based APS cluster constitutes a hybrid of an industrial complex with stable formal ties and a social network based on informal exchange. Financial services assume a central position in what might be called ‘a para-financial services complex’, revealing close ties with legal services, accountancy and audit, and ICT. Geographically, we find that the APS complex depends on fine-grained localisation economies, which allow a small share of APS professionals to service both domestic and international clients. We conclude that APS actors in Brussels exhibit a strong domestic anchoring, indicative of the continued relevance of world cities as national financial centres amidst financial globalisation.
