  We report the discovery, using NICMOS on the Hubble Space Telescope, of an
arcsecond-diameter Einstein ring in the gravitational lens system B1938+666.
The lensing galaxy is also detected, and is most likely an early-type.
Modelling of the ring is presented and compared with the radio structure from
MERLIN maps. We show that the Einstein ring is consistent with the
gravitational lensing of an extended infrared component, centred between the
two radio components.
