A method (10, 30, 60, 70) of manufacturing an RFID tag assembly, the method comprising: providing (12, 32) a mounting base made of an electrically conductive material; providing a passive mount-on-metal RFID tag, the RFID tag comprising an integrated circuit chip provided at a first position and an antenna provided on one side; mounting the RFID tag on the mounting base with said one side of the RFID tag coupled to a first side of the mounting base, to form an RFID tag-mounting base sub-assembly; providing (16, 34, 42, 62) a mould tool comprising a mould cavity shaped to form a cover of the RFID tag assembly and locating the RFID tag-mounting base sub-assembly within the mould cavity such that a void defining the cover is formed between the mould tool and the RFID tag-mounting base sub-assembly; and delivering (18, 36, 44, 64, 72, 76) a substantially RF transparent material in a molten state into the void between the mould tool and the RFID tag-mounting base sub-assembly and allowing the substantially RF transparent material to cool into a solid state, to thereby form a cover over the RFID tag-mounting base sub-assembly, such that the mounting base and the cover together encapsulate the RFID tag, wherein the substantially RF transparent material has a temperature in the molten state on delivery into the void that is higher than a maximum tolerable temperature of the integrated circuit chip and the substantially RF transparent material is delivered into the void at a second position away from first position and wherein the mould tool is configured to cause the substantially RF transparent material to cool as it flows towards the first position such that the temperature of the substantially RF transparent material does not exceed the maximum tolerable temperature of the integrated circuit chip when the substantially RF transparent material reaches the first position. providing (12, 32) a mounting base made of an electrically conductive material; providing a passive mount-on-metal RFID tag, the RFID tag comprising an integrated circuit chip provided at a first position and an antenna provided on one side; mounting the RFID tag on the mounting base with said one side of the RFID tag coupled to a first side of the mounting base, to form an RFID tag-mounting base sub-assembly; providing (16, 34, 42, 62) a mould tool comprising a mould cavity shaped to form a cover of the RFID tag assembly and locating the RFID tag-mounting base sub-assembly within the mould cavity such that a void defining the cover is formed between the mould tool and the RFID tag-mounting base sub-assembly; and delivering (18, 36, 44, 64, 72, 76) a substantially RF transparent material in a molten state into the void between the mould tool and the RFID tag-mounting base sub-assembly and allowing the substantially RF transparent material to cool into a solid state, to thereby form a cover over the RFID tag-mounting base sub-assembly, such that the mounting base and the cover together encapsulate the RFID tag, wherein the substantially RF transparent material has a temperature in the molten state on delivery into the void that is higher than a maximum tolerable temperature of the integrated circuit chip and the substantially RF transparent material is delivered into the void at a second position away from first position and wherein the mould tool is configured to cause the substantially RF transparent material to cool as it flows towards the first position such that the temperature of the substantially RF transparent material does not exceed the maximum tolerable temperature of the integrated circuit chip when the substantially RF transparent material reaches the first position.