We announce the discovery of an extended emission line region associated with a high redshift type-2 QSO .
The halo , which was discovered in our new wide-field narrow-band survey , resides at z = 2.85 in the Spitzer First Look Survey region and is extended over \sim 80 kpc .
Deep VLBI observations imply that approximately 50 per cent of the radio emission is extended on scales > 200pc .
The inferred AGN luminosity is sufficient to ionize the extended halo , and the optical emission is consistent with being triggered coevally with the radio source .
The Lyman- \alpha halo is as luminous as those found around high redshift radio galaxies , however the active nucleus is several orders of magnitude less luminous at radio wavelengths than those FRIIs more commonly associated with extended emission line regions .
AMS05 appears to be a high-redshift analogue to the radio-quiet quasar E1821+643 which is core dominated but which also exhibits extended FRI-like structure and contains an optically powerful AGN .
We also find evidence for more quiescent kinematics in the Lyman- \alpha emission line in the outer regions of the halo , reminiscent of the haloes around the more powerful FRIIs .
The optical to mid-infrared SED is well described by a combination of an obscured QSO ( L _ { bol } \sim 3.4 \pm 0.2 \times 10 ^ { 13 } L _ { \odot } ) and a 1.4 Gyr old simple stellar population with mass \sim 3.9 \pm 0.3 \times 10 ^ { 11 } M _ { \odot } .