MATS prt 1 section 3 chapter Page 10
Visual Approach
To expedite traffic at any time, IFR flights may be authorised to execute visual approaches if the pilot reports he can maintain visual reference to the surface and
a) the reported cloud ceiling is not below the initial approach level; or
b) the pilot reports at any time after commencing the approach procedure that the visibilitywill permit a visual approach and landing, and a reasonable assurance exists that this can be accomplished.
Standard separation shall be effected between such aircraft and othe IFR and/or SVFR aircraft