1. Signed, written informed consent

          2. Subjects must be willing and able to comply with scheduled visits and procedures

          3. Histologically confirmed squamous cell carcinoma of the oral cavity, (oral tongue
             (anterior 2/3), gingiva/alveolus, floor of mouth, buccal sulcus, retromolar trigone,
             and hard palate as defined by ICD-10 codes)

          4. Subjects willing to have a fresh biopsy performed, or archival tissue available from
             diagnostic biopsy meeting requirements set out in laboratory manual.

          5. Clinically and/or radiologically staged as T1-4 N1-3 or any T3-4 N0 (unless T4 on the
             basis of bone invasion only). Staging based upon the AJCC/UICC TNM 8th Edition.

          6. Surgery planned as primary treatment modality with patients fit for major resection ±
             reconstruction surgical procedure.

          7. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

          8. 18 years or over at time of provision of consent for trial inclusion.

          9. Screening laboratory values must meet the following criteria

               -  WBC ≥ 2000/µL

               -  Neutrophils ≥ 1500/uL

               -  Platelets ≥ 100x103/uL

               -  Hemoglobin ≥ 9.0 g/dL

               -  Serum creatinine ≤ 1.5 x ULN or calculated creatinine clearance > 40 mL/min
                  (using the Cockcroft-Gault formula)

               -  AST ≤ 3.0 x ULN

               -  ALT ≤ 3.0 x ULN

               -  Total Bilirubin ≤ 1.5 x ULN (except subjects with Gilbert Syndrome who must have
                  a total bilirubin level of < 3.0x ULN).

         10. Women of childbearing potential (WOCBP) must have a negative serum or urine pregnancy
             test (minimum sensitivity 25 IU/L or equivalent units of HCG) within 24 hours prior to
             the start of study drug.

         11. Women must not be breastfeeding

         12. WOCBP must agree to follow instructions for method(s) of contraception for a period of
             30 days (duration of ovulatory cycle) plus the time required for the investigational
             drug to undergo approximately five half-lives. WOCBP randomized/assigned to receive
             nivolumab should use an adequate method to avoid pregnancy for 5 months (30 days plus
             the time required for nivolumab to undergo approximately five half-lives) after the
             last dose of investigational drug.

         13. Males who are sexually active with WOCBP must agree to follow instructions for
             method(s) of contraception for a period of 90 days (duration of sperm turnover) plus
             the time required for the investigational drug to undergo approximately five
             half-lives

         14. Males randomized to receive nivolumab who are sexually active with WOCBP must continue
             contraception for 7 months (90 days plus the time required for nivolumab to undergo
             approximately five half-lives) after the last dose of investigational drug.
             Azoospermic males and WOCBP who are continuously not heterosexually active are exempt
             from contraceptive requirements. However they must still undergo pregnancy testing as
             described in these sections. Investigators shall counsel WOCBP and male subjects who
             are sexually active with WOCBP on the importance of pregnancy prevention and the
             implications of an unexpected pregnancy Investigators shall advise WOCBP and male
             subjects who are sexually active with WOCBP on the use of highly effective methods of
             contraception. Highly effective methods of contraception which have a failure rate of
             < 1% when used consistently and correctly

        Exclusion Criteria:

          1. Tumours staged as T4 on the basis of bone invasion only and in the absence of nodal
             metastases.

          2. Distant metastases detected, or suspected on imaging

          3. Unfit for chemoradiotherapy, due to comorbidity.

          4. Previous malignancy requiring treatment within the last 3 years (with the exception of
             non-melanoma skin cancers, and the following in situ cancers: bladder, gastric, colon,
             oesophageal endometrial, cervical/dysplasia, melanoma, or breast). Prior head and neck
             cancer within the last three years is allowed if the tumour was treated with surgery
             only, and did not require radiotherapy.

          5. Prior head and neck radiotherapy

          6. On immunosuppressive medication (including steroids at dose equivalent to prednisolone
             >10mg/day unless used as replacement therapy).

          7. Subjects with an active, known or suspected autoimmune disease. Subjects with type I
             diabetes mellitus, hypothyroidism only requiring hormone replacement, skin disorders
             (such as vitiligo, psoriasis, or alopecia) not requiring systemic treatment, lichen
             planus or other conditions not expected to recur in the absence of an external trigger
             are permitted to enrol.

          8. Known human immunodeficiency virus (HIV) or viral hepatitis infection.

          9. Women who are pregnant or breastfeeding

         10. Known medical condition that, in the investigator's opinion, would increase the risk
             associated with study participation or study drug administration or interfere with the
             interpretation of safety results.