We numerically explore the many body localization (MBL) transition through
the lens of the {\it entanglement spectrum}. While a direct transition from
localization to thermalization is believed to obtain in the thermodynamic limit
(the exact details of which remain an open problem), in finite system sizes
there exists an intermediate `quantum critical' regime. Previous numerical
investigations have explored the crossover from thermalization to criticality,
and have used this to place a numerical {\it lower} bound on the critical
disorder strength for MBL. A careful analysis of the {\it high energy} part of
the entanglement spectrum (which contains universal information about the
critical point) allows us to make the first ever observation in exact numerics
of the crossover from criticality to MBL and hence to place a numerical {\it
upper bound} on the critical disorder strength for MBL.Comment: 4 pages+appendi
