Vascular Targeted Photodynamic therapy (VTP) with the Vascular Occluding Agent (VOA) WST11, may offer an alternative, providing tumour destruction via a minimally invasive approach. In this investigation, the investigators plan to use the WST11 VTP procedure to treat a predetermined small renal tumour targets. Patients will be given a general anaesthetic, to ensure immobility, and prevent discomfort during treatment sessions. Treated patients will then undergo surgical resection of their tumours, and the accuracy and reliability of tissue death with VTP will be assessed histologically. The aim of this proof of concept study is to demonstrate whether this modality has potential for a clinical role in the treatment of oncological kidney disease, either as an alternative to surgery, or where surgery is not feasible.