We have used spectra obtained with X-shooter , the triple arm optical-infrared spectrograph recently commissioned on the Very Large Telescope ( VLT ) of the European Southern Observatory ( ESO ) , to confirm the gravitational lens nature of the CASSOWARY candidate CSWA 20 . This system consists of a luminous red galaxy at redshift z _ { abs } = 0.741 , with a very high velocity dispersion , \sigma _ { lens } \simeq 500 km s ^ { -1 } , which lenses a blue star-forming galaxy at z _ { em } = 1.433 into four images with mean separation of \sim 6 ^ { \prime \prime } . The source shares many of its properties with those of UV-selected galaxies at z = 2 –3 : it is forming stars at a rate \textrm { SFR } \simeq 25 M _ { \odot } yr ^ { -1 } , has a metallicity of \sim 1 / 4 solar , and shows nebular emission from two components separated by 0.4 ^ { \prime \prime } ( in the image plane ) , possibly indicating a merger . It appears that foreground interstellar material within the galaxy has been evacuated from the sight-line along which we observe the starburst , giving an unextinguished view of its stars and H ii regions . CSWA 20 , with its massive lensing galaxy producing a high magnification of an intrinsically luminous background galaxy , is a promising target for future studies at a variety of wavelengths .