A computer system for supporting multiple enterprise networks (100, 180) in connecting to virtual desktops hosted on a plurality of host machines, each enterprise network (100, 180) including computer resources (102, 182), the computer system comprising: a virtual local area network for each enterprise network (100, 180), each virtual local area network being connected to a plurality of the host machines for the enterprise network (100, 180), each host machine supporting desktops for use by the enterprise network (100, 180), the desktops accessing the computer resources (102, 182) on the enterprise network (100, 180) to which it is connected; and a router connected to the enterprise networks (100, 180) and comprising a virtual router for each said enterprise network (100, 180), including a distinct routing table for each enterprise network (100, 180), for routing traffic between the desktops hosted on the plurality of host machines and the computer resources (102, 182) on the enterprise networks (100, 180), wherein one or more of the host machines includes a virtual switch for each of a plurality of the enterprise networks (100, 180), wherein the virtual switch for each said enterprise network (100, 180) is connected to the virtual local area network of the enterprise network (100, 180) and to the desktops in the host machine which are allocated to the respective enterprise network (100, 180); and characterised in that the computer system further comprises: a resource manager which is arranged to manage allocation of the host machines to the enterprise networks (100, 180) and allocation of the desktops to the enterprise networks (100, 180); wherein the resource manager comprises: a service provider management tool which is used by a service provider to allocate a quota of infrastructure capacity of the host machines to each said enterprise network (100, 180); and a tenant management tool which is used by a tenant to allocate desktop capacity to their respective enterprise network (100, 180) within the previously allocated quota of the infrastructure capacity of the host machines. a virtual local area network for each enterprise network (100, 180), each virtual local area network being connected to a plurality of the host machines for the enterprise network (100, 180), each host machine supporting desktops for use by the enterprise network (100, 180), the desktops accessing the computer resources (102, 182) on the enterprise network (100, 180) to which it is connected; and a router connected to the enterprise networks (100, 180) and comprising a virtual router for each said enterprise network (100, 180), including a distinct routing table for each enterprise network (100, 180), for routing traffic between the desktops hosted on the plurality of host machines and the computer resources (102, 182) on the enterprise networks (100, 180), wherein one or more of the host machines includes a virtual switch for each of a plurality of the enterprise networks (100, 180), wherein the virtual switch for each said enterprise network (100, 180) is connected to the virtual local area network of the enterprise network (100, 180) and to the desktops in the host machine which are allocated to the respective enterprise network (100, 180); and characterised in that the computer system further comprises: a resource manager which is arranged to manage allocation of the host machines to the enterprise networks (100, 180) and allocation of the desktops to the enterprise networks (100, 180); wherein the resource manager comprises: a service provider management tool which is used by a service provider to allocate a quota of infrastructure capacity of the host machines to each said enterprise network (100, 180); and a tenant management tool which is used by a tenant to allocate desktop capacity to their respective enterprise network (100, 180) within the previously allocated quota of the infrastructure capacity of the host machines. a resource manager which is arranged to manage allocation of the host machines to the enterprise networks (100, 180) and allocation of the desktops to the enterprise networks (100, 180); wherein the resource manager comprises: a service provider management tool which is used by a service provider to allocate a quota of infrastructure capacity of the host machines to each said enterprise network (100, 180); and a tenant management tool which is used by a tenant to allocate desktop capacity to their respective enterprise network (100, 180) within the previously allocated quota of the infrastructure capacity of the host machines. a service provider management tool which is used by a service provider to allocate a quota of infrastructure capacity of the host machines to each said enterprise network (100, 180); and a tenant management tool which is used by a tenant to allocate desktop capacity to their respective enterprise network (100, 180) within the previously allocated quota of the infrastructure capacity of the host machines.