A portable navigation device, comprising: an alert content reception apparatus comprising: a communications interface compatible with a data broadcast service and a wireless bidirectional data communications service; and a processing resource; a receiver of location-related data, the receiver being operably coupled to the processing resource; and a memory resource, the communications interface being arranged to receive broadcast data messages from the data broadcast service, each broadcast data message comprising: reference data identifying alert content stored at a remote server apparatus; and geographical indication data identifying a location associated with the alert content, the processing resource being arranged to: analyse a received broadcast data message to determine the reference data and the geographical indication data; compare the determined reference data to a list of reference data from previously received broadcast data messages stored in the memory resource; determine a current location of the portable navigation device from received location-related data; and generate a request message comprising the reference data for transmittal by the communications interface in response to determining that the reference data has not been previously received and determining that the location associated with the alert content is within a predetermined distance of the current location of the portable navigation device, the communications interface being further arranged to: transmit the generated request message via the bidirectional data communications service to retrieve the alert content associated with the reference data in the request message from the remote server apparatus; and receive a reply message from the remote server apparatus via the bidirectional data communications service, the reply message comprising the alert content associated with the reference data in the request message. an alert content reception apparatus comprising: a communications interface compatible with a data broadcast service and a wireless bidirectional data communications service; and a processing resource; a receiver of location-related data, the receiver being operably coupled to the processing resource; and a memory resource, the communications interface being arranged to receive broadcast data messages from the data broadcast service, each broadcast data message comprising: reference data identifying alert content stored at a remote server apparatus; and geographical indication data identifying a location associated with the alert content, the processing resource being arranged to: analyse a received broadcast data message to determine the reference data and the geographical indication data; compare the determined reference data to a list of reference data from previously received broadcast data messages stored in the memory resource; determine a current location of the portable navigation device from received location-related data; and generate a request message comprising the reference data for transmittal by the communications interface in response to determining that the reference data has not been previously received and determining that the location associated with the alert content is within a predetermined distance of the current location of the portable navigation device, analyse a received broadcast data message to determine the reference data and the geographical indication data; compare the determined reference data to a list of reference data from previously received broadcast data messages stored in the memory resource; determine a current location of the portable navigation device from received location-related data; and generate a request message comprising the reference data for transmittal by the communications interface in response to determining that the reference data has not been previously received and determining that the location associated with the alert content is within a predetermined distance of the current location of the portable navigation device, the communications interface being further arranged to: transmit the generated request message via the bidirectional data communications service to retrieve the alert content associated with the reference data in the request message from the remote server apparatus; and receive a reply message from the remote server apparatus via the bidirectional data communications service, the reply message comprising the alert content associated with the reference data in the request message. transmit the generated request message via the bidirectional data communications service to retrieve the alert content associated with the reference data in the request message from the remote server apparatus; and receive a reply message from the remote server apparatus via the bidirectional data communications service, the reply message comprising the alert content associated with the reference data in the request message.