We obtained Subaru FMOS observations of Halpha emitting galaxies selected from the HiZELS narrow-band survey, to investigate the relationship between stellar mass, metallicity and star-formation rate at z = 0.84 - 1.47, for comparison with the Fundamental Metallicity Relation seen at low redshift. Our findings demonstrate, for the first time with a homogeneously selected sample, that a relationship exists for typical star-forming galaxies at z = 1 - 1.5 and that it is surprisingly similar to that seen locally. Therefore, star-forming galaxies at z = 1 - 1.5 are no less metal abundant than galaxies of similar mass and star formation rate (SFR) at z = 0.1, contrary to claims from some earlier studies. We conclude that the bulk of the metal enrichment for this star-forming galaxy population takes place in the 4 Gyr before z = 1.5. We fit a new mass-metallicity-SFR plane to our data which is consistent with other high redshift studies. However, there is some evidence that the mass-metallicity component of this high redshift plane is flattened, at all SFR, compared with z = 0.1, suggesting that processes such as star-formation driven winds, thought to remove enriched gas from low mass halos, are yet to have as large an impact at this early epoch. The negative slope of the SFR-metallicity relation from this new plane is consistent with the picture that the elevation in the SFR of typical galaxies at z > 1 is fuelled by the inflow of metal-poor gas and not major merging.
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