Design and methods: After numbing the skin with local anaesthetic, a specialist doctor (radiologist) or trained radiographer will use ultrasound to guide the injection of a small volume of dilute (0.5%) hydrogen peroxide solution into the tumour twice a week during 3 weeks of standard radiotherapy. The drug is suspended in a natural gel (1% sodium hyaluronate, licensed for treating stiff knee joints) that ensures its slow release over 48 hours. The injection procedure lasts for 10-15 minutes altogether. Tiny oxygen bubbles are released from the hydrogen peroxide which help the radiologist guide the injection of drug to the proper places under the skin. The investigators want to test this approach, starting with a careful study of side effects in 12 patients (pilot study) followed by a randomised trial in 84 patients to test activity against cancer (Phase II). Patients participating in Phase II will either have standard radiotherapy or the same radiotherapy plus the drug under test. Neither the patient nor the doctor will choose who has which treatment, which is allocated randomly. Review of the Pilot study data by an independent committee of experts will be completed before starting the phase II (efficacy) study.