Reassessment of absorbed dose to LiF/Polytetrafluorethylene dosimeter by photo-transferred thermoluminescence (PTTL) is made routinely as part of the National Radiological Protection Board Thermoluminescence Dosimetry Service to confirm doses greater than 20 mSv(2 rem). Reassessment by PTTL involves the transfer of charge carriers, which remain in deep traps during the normal readout cycle, to the dosimetry traps by the action of ultra-violet radiation.