This article examines the problems that existed for British policy makers in their attempts to build a consistent and coherent long term policy towards the Soviet Union while balancing competing objectives such as maintaining an anti-revisionist stance against aggressor states. It argues, first, that the 1939 guarantee to Romania was an instrument of declaratory politics for Britain that represented a statement against changes by force, but not revision writ large and, second, that it undermined British efforts to provoke Romanian resistance in 1940. In both cases, this was largely because Germany and Romania correctly perceived that there was no genuine Anglo-Soviet understanding to underpin it.