The unit of randomisation will be the individual research participant. After stratification by centre, by HbA1c level (HbA1c < 38mmol/mol or ≥ 38mmol/mol), BMI level (BMI < 30 kg/m2 or ≥ 30 kg/m2) and previous response to NB-UVB (achieved remission within 25 exposures during most recent course of NBUVB or not) 120 research participants will be assigned randomly, in a ratio of 1:1 using blocks of 2, to receive either: