Inclusion Criteria:  Written informed consent for the trial. Aged ≥18 years Willing to provide tissue from an excisional biopsy of a tumor lesion Confirmed diagnosis of HCC. The diagnosis can be established radiographically by the criteria of the American Association for the Study of the Liver (AASLD), or by histologic diagnosis from the core biopsy. Have measurable disease by Computed Tomography (CT)-scan or Magnetic Resonance Imaging (MRI) defined by RECIST (Response Evaluation Criteria In Solid Tumours) 1.1 criteria and HCC specific mRECIST (modified RECIST). Medically fit to undergo surgery as determined by the treating medical and surgical oncology team ECOG (Eastern Cooperative Oncology Group) performance status 0 or 1 Adequate organ and marrow function as defined below:  1) leukocytes ≥3,000/mcL 2) absolute neutrophil count ≥1,500/mcL 3) platelets ≥100,000/mcL 4) total bilirubin ≤ 2 × institutional upper limit of normal (ULN) 5) AST (aspartate aminotransferase)/ALT(alanine aminotransferase) ≤ 3 × institutional ULN 6) creatinine ≤ 1.5 × institutional ULN OR 7) estimated glomerular filtration rate (GFR) ≥50 mL/min/1.73 m2 (according to the Cockcroft-Gault formula) 9. Overall Child-Pugh class A 10. Documented virology status of hepatitis, as confirmed by screening tests for HBV (hepatitis B virus) and HCV (hepatitis C virus)  For patients with active HBV: HBV DNA <2000 IU/mL during screening, and have initiated anti-HBV treatment at least 14 days prior to SBRT and willingness to continue anti-HBV treatment during the study (per local standard of care; e.g., entecavir). Patients with HCV, either with resolved infection (as evidenced by detectable antibody and negative viral load) or chronic infection (as evidenced by detectable HCV RNA), are eligible.  11. Participants with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial.  12. Female patient of childbearing potential should have a negative serum pregnancy test within 24 h of her first dose of IMP (Investigational Medicinal Product) 13. Women of childbearing potential must be willing to use a highly effective method of contraception for the course of the study through 5 months after the last dose of IMP. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the patient.  14. Sexually active males must agree to use an adequate method of contraception starting with the first dose of IMP through 7 months after the last dose of study therapy. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the patient.  Exclusion Criteria:  Extrahepatic metastasis Prior systemic anticancer treatment for HCC, including an anti-PD-1, anti-PD-L1 or anti-CTLA-4 antibody Prior orthotopic liver transplantation Prior abdominal irradiation Any major surgery within the 3 weeks prior to enrolment Hepatic encephalopathy Ascites that is refractory to diuretic therapy Is currently receiving anti-cancer therapy (chemotherapy, radiation therapy, immunotherapy or biologic therapy) or has participated or is participating in a study of an IMP or used an investigational device within 4 weeks of the first dose of IMP Diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy Known history of active Bacillus Tuberculosis (TB) History of known hypersensitivity to any monoclonal antibody or any of their excipients Known additional malignancy that is progressing or requires active treatment. Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative therapy, or in situ cervical cancer Active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Replacement therapy (eg. thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment Active infection requiring systemic therapy, with exceptions relating to Hepatitis B and C virus infection History or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the patient's participation for the full duration of the trial, or is not in the best interest of the patient to participate, in the opinion of the treating Principal Investigator (PI) Known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial Pregnant or breastfeeding Known history of Human Immunodeficiency Virus (HIV; HIV 1/2 antibodies) Received a live vaccine within 30 days of first dose of IMP administration.