In many distributed systems applications deployed on the worldwide scale, it is latency, rather than bandwidth, that is the primary determinant of performance. This paper describes Ambassadors, a communication technique using mobile Java objects within an RPC/RMI-like communication structure. Ambassadors minimise the aggregate latency of sequences of inter-dependent remote operations by migration of code to the vicinity of the server to execute those operations. Furthermore, because Ambassadors migrate within an RPC/RMI-like structure, communication has well defined failure semantics, an important characteristic in supporting effective software engineering of distributed systems.