We have searched the WISE first data release for widely separated ( \leq 10,000AU ) late T dwarf companions to Hipparcos and Gliese stars .
We have discovered a new binary system containing a K-band suppressed T8p dwarf WISEP J1423+0116 and the mildly metal poor ( [ Fe/H ] = - 0.38 \pm 0.06 ) primary BD+01 2920 ( Hip 70319 ) , a G1 dwarf at a distance of 17.2pc .
This new benchmark has T _ { eff } =680 \pm 55K and a mass of 20 - 50 M _ { Jup } .
Its spectral properties are well modelled except for known discrepancies in the Y and K bands .
Based on the well determined metallicity of its companion , the properties of BD+01 2920B imply that the currently known T dwarfs are dominated by young low-mass objects .
We also present an accurate proper motion for the T8.5 dwarf WISEP J075003.84+272544.8 .