Prostate SABR With Intra-Prostatic SABR Boost

Inclusion Criteria: * Histologically confirmed prostate adenocarcinoma * High-risk prostate cancer, defined as at least one of: T3, Gleason 8-10, OR PSA \> 20 ng/mL * Willing to give informed consent to participate in this clinical trial Exclusion Criteria: * Prior pelvic radiotherapy * Contraindication to radical prostate radiotherapy e.g. connective tissue disease or inflammatory bowel disease * Contraindication to prostate MRI * No evidence of castrate resistance (defined as PSA \< 3 ng/ml while testosterone is \< 0.7nmol/l. Patients could have been on combined androgen blockade but are excluded if this was started due to PSA progression. * Definitive extrapelvic nodal or distant metastatic disease on staging investigations.