  We report the discovery of ULAS J131610.28+075553.0, a sdT6.5 dwarf in the
UKIDSS Large Area Survey 2 epoch proper motion catalogue. This object displays
significant spectral peculiarity, with the largest yet seen deviations from T6
and T7 templates in the Y and K bands for this subtype. Its large, ~1
arcsec/yr, proper motion suggests a large tangential velocity of Vtan = 240 -
340km/s, if we assume its MJ lies within the typical range for T6.5 dwarfs.
This makes it a candidate for membership of the Galactic halo population.
However, other metal poor T dwarfs exhibit significant under luminosity both in
specific bands and bolometrically. As a result, it is likely that its velocity
is somewhat smaller, and we conclude it is a likely thick disc or halo member.
This object represents the only T dwarf earlier than T8 to be classified as a
subdwarf, and is a significant addition to the currently small number of known
unambiguously substellar subdwarfs.
