Terahertz (THz) science and technology has experienced tremendous progress in recent years, such as in spectroscopy, imaging, pharmaceutical research [1] and wireless communications. These applications require electrically tuneable devices to modulate the THz properties, including the amplitude, frequency and polarization. The integration of resonant plasmonic/metamaterial devices with graphene, has proved a successful route for the realisation of fast reconfigurable, efficient THz optoelectronic devices [2], via electrical tuning of graphene integrated with plasmonic resonant structures.