A communication system, comprising: a first computing device having a sensor (30, 30') and a display; a second computing device having a display; a data service configured to mediate communication between the first and second computing devices (12; 14); wherein the first computing device is configured to generate control data by decoding information embodied in a contactlessly readable identification device scanned with the sensor (30, 30'), the identification device having address data indicative of an authentication server and identification data associated with a user of a second computing device, such that the control data comprises the address data and the identification data; the first computing device configured to: a) respond to the control data by transmitting an authentication request to the authentication server, the authentication request comprising at least the identification data, b) respond to receiving an authentication and/or access token from the authentication server by transmitting a contact data request for contact data associated with the identification data to the data service, the contact data being configured to allow the first computing device to establish communication with the second computing device, and the contact data request including the token, and c) respond to receiving the contact data from the data service by transmitting a communication request to the data service according to the contact data, characterized in that the communication request is configured to prompt the data service to generate and issue a user alert or notification identifying at least a mode of communication and a user operable acceptance mechanism (190, 192) operable to control the second computing device to open or accept the mode of communication with the first computing device. a first computing device having a sensor (30, 30') and a display; a second computing device having a display; a data service configured to mediate communication between the first and second computing devices (12; 14); wherein the first computing device is configured to generate control data by decoding information embodied in a contactlessly readable identification device scanned with the sensor (30, 30'), the identification device having address data indicative of an authentication server and identification data associated with a user of a second computing device, such that the control data comprises the address data and the identification data; the first computing device configured to: a) respond to the control data by transmitting an authentication request to the authentication server, the authentication request comprising at least the identification data, b) respond to receiving an authentication and/or access token from the authentication server by transmitting a contact data request for contact data associated with the identification data to the data service, the contact data being configured to allow the first computing device to establish communication with the second computing device, and the contact data request including the token, and c) respond to receiving the contact data from the data service by transmitting a communication request to the data service according to the contact data, characterized in that the communication request is configured to prompt the data service to generate and issue a user alert or notification identifying at least a mode of communication and a user operable acceptance mechanism (190, 192) operable to control the second computing device to open or accept the mode of communication with the first computing device. a) respond to the control data by transmitting an authentication request to the authentication server, the authentication request comprising at least the identification data, b) respond to receiving an authentication and/or access token from the authentication server by transmitting a contact data request for contact data associated with the identification data to the data service, the contact data being configured to allow the first computing device to establish communication with the second computing device, and the contact data request including the token, and c) respond to receiving the contact data from the data service by transmitting a communication request to the data service according to the contact data,