A Radio Frequency Identification (RFID) tag has an electronic identification circuit coupled to an antenna, wherein the RFID tag is arranged to communicate with a RFID tag reader via the antenna, using RF energy. The tag comprises means sensitive to light (such as a photodiode, phototransistor, photocell or a solar cell) for controlling (in particular inhibiting) communication between the RFID tag reader and the RFm tag. The tag can for example be embedded in or on a high-value object such as a banknote. The existence of the banknote cannot be detected e.g. by criminals in the absence of light (e.g. while the banknote is located in a wallet), but the authenticity of the banknote can be verified in legitimate use.