Controlling carrier selection in a wireless communication system

A mobile communications system comprising:

• an arrangement of at least one base station configured to communicate data to and/or from different types of terminal device via respective ones of a plurality of logically separate carriers of a wireless access interface;
• a first terminal device operable to camp-on to a first carrier of the plurality of carriers and to subsequently communicate data with the arrangement of at least one base station via the first carrier, and
• a second terminal device operable to camp-on to a second carrier of the plurality of carriers and to subsequently communicate data with the arrangement of at least one base station via the second carrier, wherein
• the first and second carriers support compatible synchronisation signalling such that the first and second terminal devices can both synchronise with the first and second carriers to begin a camp-on procedure, but wherein the first and second carriers support incompatible physical layer signalling associated with control channels of their respective camp-on procedures such that the first terminal device is unable to complete a camp-on procedure with the second carrier.