  We present initial results of a new, systematic search for massive
star-formation in the host galaxies of the most luminous and probably most
massive z>=4 radio-quiet quasars (M(B) <= -27.5; nuL(nu)(1450Ang)>10^13Lsun).
  A total of 38 z>=4 radio-quiet quasars have been observed at the JCMT using
SCUBA at 850microns: 8 were detected (>3sigma) with S(850microns)>~ 10mJy
(submillimetre-loud). The new detections almost triple the number of optically
selected, submillimetre-loud z>~4 radio-quiet quasars known to date. We include
a detailed description of how our quasar sample is defined in terms of radio
and optical properties.
  There is no strong evidence for trends in either detectability or 850microns
flux with absolute magnitude, M(B). We find that the weighted mean flux of the
undetected sources is 2.0 +/- 0.6mJy, consistent with an earlier estimate of
\~3mJy based on more sensitive observations of a sample z>~4 radio-quiet
quasars (McMahon et al., 1999). This corresponds to an inferred starformation
rate of \~1000Msun/yr, similar to Arp220. The typical starformation timescale
for the submillimetre-bright sources is ~1Gyr, 10 times longer than the typical
accretion-driven e-folding timescale of ~5x10^7 years. Our 850micron detection
of the z=4.4 quasar PSS J1048+4407 when analysed in conjunction with 1.2mm
single-dish and interferometric observations suggests that this source is
resolved on angular scales of 1-2" (6-12 kpc). In addition, we present a new
optical spectrum of this source, identifying it as a broad absorption line
(BAL) quasar. The new redshift is outside that covered in a recent CO line
search by Guilloteau et al., (1999), highlighting the need for accurate
redshifts for the obervation and interpretation of high-redshift line studies.
