A method of monitoring objects such as offenders, the method including the steps of: providing an electronic monitoring device for attachment to an object to be monitored; providing a tamper evident tether for attachment of the electronic monitoring device to the object to be monitored; attaching the electronic monitoring device to the object to be monitored using the tamper evident tether; and remotely monitoring the electronic monitoring device in order to monitor the location of the object; the method further including the steps of: providing the tamper evident tether with a unique identifier; providing an electronic data store remote from the electronic monitoring device; recording the unique identifier for the tether in the electronic data store, together with information about the object to be monitored and/or the associated electronic monitoring device; and performing an interrogation step at least once after the date on which the electronic monitoring device is first attached to the object, to determine whether the tether associated with the electronic monitoring device has the same unique identifier as that recorded in the electronic data store; the method being characterised by: the unique identifier being provided at a first end of the tether, and the method including the step of fitting said first end to the electronic monitoring device, so that the unique identifier is hidden within the electronic monitoring device. providing an electronic monitoring device for attachment to an object to be monitored; providing a tamper evident tether for attachment of the electronic monitoring device to the object to be monitored; attaching the electronic monitoring device to the object to be monitored using the tamper evident tether; and remotely monitoring the electronic monitoring device in order to monitor the location of the object; the method further including the steps of: providing the tamper evident tether with a unique identifier; providing an electronic data store remote from the electronic monitoring device; recording the unique identifier for the tether in the electronic data store, together with information about the object to be monitored and/or the associated electronic monitoring device; and performing an interrogation step at least once after the date on which the electronic monitoring device is first attached to the object, to determine whether the tether associated with the electronic monitoring device has the same unique identifier as that recorded in the electronic data store; providing the tamper evident tether with a unique identifier; providing an electronic data store remote from the electronic monitoring device; recording the unique identifier for the tether in the electronic data store, together with information about the object to be monitored and/or the associated electronic monitoring device; and performing an interrogation step at least once after the date on which the electronic monitoring device is first attached to the object, to determine whether the tether associated with the electronic monitoring device has the same unique identifier as that recorded in the electronic data store; the method being characterised by: the unique identifier being provided at a first end of the tether, and the method including the step of fitting said first end to the electronic monitoring device, so that the unique identifier is hidden within the electronic monitoring device. the unique identifier being provided at a first end of the tether, and the method including the step of fitting said first end to the electronic monitoring device, so that the unique identifier is hidden within the electronic monitoring device.