The ability to dynamically create and subsequently manage secure virtual organisations (VO) is one of the key challenges facing the Grid community. Existing approaches for establishing and managing VOs typically suffer from lack of fine grained security since they largely focus on public key infrastructures with statically defined access control lists, or they are based upon a centralised site for storage of VO specific security information. What is really needed is a federated model of security where sites are able to manage their own security information for their own institutional members, delegating where necessary to trusted local or remote entities, as well as defining and enforcing authorisation policies for their own resources. In this paper we present tools that support such capabilities and highlight how they have been applied to dynamically create and manage security focused VOs in the education domain. We believe that this federated VO security model for fine grained access to Grid services and resources should be the future model upon which security focused Grids are based.