Unitals in PG(2,q2) with a large 2-point stabiliser

Let UU be a unital embedded in the Desarguesian projective plane PG(2,q2). Write MM for the subgroup of PGL(3,q2) which preserves UU. We show that UU is classical if and only if UU has two distinct points P,QP,Q for which the stabiliser G=MP,QG=MP,Q has order q2−1q2−1.