Observations of radio-quiet quasars at 10mas resolution by use of
  gravitational lensing
  We present VLA detections of radio emission in four four-image gravitational
lens systems with quasar sources: HS0810+2554, RXJ0911+0511, HE0435$-$1223 and
SDSSJ0924+0219, and e-MERLIN observations of two of the systems. The first
three are detected at a high level of significance, and SDSS J0924+0219 is
detected. HS0810+2554 is resolved, allowing us for the first time to achieve
10-mas resolution of the source frame in the structure of a radio quiet quasar.
The others are unresolved or marginally resolved. All four objects are among
the faintest radio sources yet detected, with intrinsic flux densities in the
range 1-5$\mu$Jy; such radio objects, if unlensed, will only be observable
routinely with the Square Kilometre Array. The observations of HS0810+2554,
which is also detected with e-MERLIN, strongly suggest the presence of a
mini-AGN, with a radio core and milliarcsecond scale jet. The flux densities of
the lensed images in all but HE0435-1223 are consistent with smooth galaxy lens
models without the requirement for smaller-scale substructure in the model,
although some interesting anomalies are seen between optical and radio flux
densities. These are probably due to microlensing effects in the optical.
