  We identify eight z>1 radio sources undetected at 850um but robustly detected
at 70um, confirming that they represent ultraluminous infrared galaxies
(ULIRGs) with hotter dust temperatures (T_dust=52+-10 K) than Submillimetre
Galaxies (SMGs) at similar luminosities and redshifts. These galaxies share
many properties with SMGs: ultra-violet (UV) spectra consistent with
starbursts, high stellar masses and radio luminosities. We can attribute their
radio emission to star formation since high-resolution MERLIN radio maps show
extended emission regions (with half light radii of 2-3kpc), which are unlikely
to be generated by AGN activity. These observations provide the first direct
confirmation of hot, dusty ULIRGs which are missed by current submillimetre
surveys. They have significant implications for future observations from the
Herschel Space Observatory and SCUBA2, which will select high redshift luminous
galaxies with less selection biases.
