  We present submillimetre photometry of 11 3CR and 6CE radio quasars of
similar 151-MHz radio luminosity and redshifts to the radio galaxies studied at
1.3<z<2 by Archibald et al. (2001). We detect all bar one quasar at 850
microns, and five quasars are confirmed as dusty hyperluminous objects by
detections at shorter wavelengths. Our observations reveal a clear difference
between the submillimetre luminosity distributions of the radio quasars and a
matched sample of radio galaxies: the quasars are ~5-times brighter than the
radio galaxies and >~2-times brighter accounting for possible synchrotron
contamination. This difference is in quantitative agreement with a
receding-torus unified scheme for radio sources in which the torus opening
angle depends on quasar optical luminosity, provided that there is a close
relationship between the optical and submillimetre luminosities. The
implication is that quasar-heated dust dominates the submillimetre emission for
powerful radio quasars at z~1.5. We find a significant anti-correlation between
submillimetre/far-infrared luminosity L_FIR and radio source age in the sense
that hyperluminous quasars tend to be associated with young (<10^7 yr) sources.
This suggests that the processes controlling L_FIR are synchronized with the
jet-triggering event and that L_FIR declines on a ~10^7 yr timescale. There is
evidence for a small amount of obscuration in the hyperluminous quasars from
reddening and associated or broad absorption lines. We speculate that shortly
after jet triggering, dust is more widely distributed than at later times and
is heated by the quasar nucleus and/or a short-lived synchronized starburst.
