and gas scaling relations with redshift, stellar mass and/or gas fraction are required in order to understand star formation throughout the Universe. In particular, such observations are vital to determine if the prescriptions for star formation which have been developed at $z$=0 can be applied to the rapidly evolving ISM of gas-rich, high-redshift galaxies [@Krumholz10; @Hopkins12b].

To gain a census of the dominant route by which galaxies assemble the bulk of their stellar mass within a well selected sample of high-redshift galaxies, we have conducted a wide field (several degree-scale) near-infrared narrow-band survey (the High-Z Emission Line Survey; HiZELS) which targets H$\alpha$ emitting galaxies in four precise ($\Delta z$=0.03) redshift slices: $z$=0.40, 0.84, 1.47 and 2.23 [@Geach08; @Sobral09; @Sobral10; @Sobral11; @Sobral12a; @Sobral12b]. This survey provides a large, star formation limited sample of identically selected H$\alpha$ emitters with properties “typical” of galaxies which will likely evolve into $\sim $L$_{\star}$ galaxies by $z$=0, but seen at a time when they are assembling the bulk of their stellar mass, and thus at a critical stage in their evolutionary history. Moreover, since HiZELS was carried out in the best-studied extra-galactic survey fields, there is a wealth of multi-wavelength data, including 16–36 medium and broad-band 