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Using the Atacama Large Millimetre/submillimeter Array (ALMA) and the Karl G.Jansky Very Large Array (VLA), we observed the Extended Green Object (EGO)G19.01$-$0.03 with sub-arcsecond resolution from 1.05 mm to 5.01 cmwavelengths. Our $\sim0.4''\sim1600$ AU angular resolution ALMA observationsreveal a velocity gradient across the millimetre core MM1, orientedperpendicular to the previously known bipolar molecular outflow, that isconsistently traced by 20 lines of 8 molecular species with a range ofexcitation temperatures, including complex organic molecules (COMs). Kinematicmodelling shows the data are well described by models that include a disc inKeplerian rotation and infall, with an enclosed mass of $40-70\mathrm{M}_{\odot}$ (within a 2000 AU outer radius) for a disc inclinationangle of $i=40^{\circ}$, of which $5.4-7.2 \mathrm{M}_{\odot}$ is attributed tothe disc. Our new VLA observations show that the 6.7 GHz Class II methanolmasers associated with MM1 form a partial ellipse, consistent with an inclinedring, with a velocity gradient consistent with that of the thermal gas. Thedisc-to-star mass ratio suggests the disc is likely to be unstable and may befragmenting into as-yet-undetected low mass stellar companions. Modelling thecentimetre--millimetre spectral energy distribution of MM1 shows the ALMA 1.05mm continuum emission is dominated by dust, whilst a free-free component,interpreted as a hypercompact HII region, is required to explain the VLA$\sim$5 cm emission. The high enclosed mass derived for a source with amoderate bolometric luminosity ($\sim$10$^{4} \mathrm{L}_{\odot}$) suggeststhat the MM1 disc may feed an unresolved high-mass binary system.

ALMA observations of the Extended Green Object G19.01$-$0.03: I. A Keplerian disc in a massive protostellar system