Open to patients undergoing any pre-operative treatment for locally advanced rectal cancer, TRIGGER is the only phase III clinical trial in the UK offering watch and wait. All patients will have post treatment MRI scans routinely performed, no change from the MERCURY trials high resolution MRI protocol is required. Patients will be randomised to either the control arm for management according to national guidelines - conventional MDT, clinical assessment post-treatment planning using the baseline MRI. Patients in the interventional arm will have their post treatment MRI scans read by a radiologist trained and supported to reliably report the mrTRG grade and have their management directed accordingly - 'Good response' (mrTRG 1\&2) - watch and wait (avoidance of surgery) offered. 'Poor response' (mrTRG 3-5) - local colorectal MDT is informed and uses information to discuss and agree next steps in treatment and surveillance. Patients are followed up for five years with QoL questionnaires completed at registration, 3 and 5 years.