Thermal ablation is an established treatment for lung cancer. It involves insertion of a applicator under image guidance into a lung tumour and destroying it with radiofrequency, microwave or cryotherapy. One of the common side effects is pneumothorax, which is a leak of gas from the lungs when it punctured. Air leak necessitates placement of a drainage tube in more than half of patients undergoing the procedure. The drain can be associated with some morbidity including pain, reduced mobility, prolonged hospital stay and infection Pleural embolization refers to the injection of substances to the linings of the lung to seal air leakage. There is published evidence in using pleural embolization with autologous blood (blood drawn up from the patient's veins) to prevent pneumothorax in patients undergoing lung biopsies. This technique is also known as pleural blood patch (PBP). A study involving more than 4000 patients found that PBP reduced the rates of pneumothorax by 35% and drain placement by 55% in lung patients. A study using prophylactic gelfoam torpedo embolization for radiofrequency ablation showed significant reduction in chest drain rates. In this study, investigators plan to evaluate the PBP using a tandem needle technique in patients undergoing lung ablation at the Oxford Thermal Ablation Service, one of the largest units in the country performing about 200 ablations per year, mostly microwave ablations. Patients will be randomized to receive lung ablation with or without the PBP. The PBP technique is easy to learn, enjoys high technical success rates and does not expose the patient to any significant additional risk. The primary outcome is the chest drains rates in the two trial groups: 1. patients undergoing lung ablation without PBP and 2. patients undergoing lung ablation with PBP. Other outcomes that would be measured include the volume of gas leakage on Computed Tomography (CT) imaging, safety profile, length of stay, feasibility of same day discharge, patient oriented outcomes including validated pain score, and institution oriented outcomes including medical costs. A positive trial could significantly reduce the side effect profile of lung ablation and hasten the patient's recovery. There could be significant savings in healthcare costs as the procedure may become safe to perform as a day procedure as opposed to an overnight procedure.