Inclusion Criteria:

          -  ≥18 years of age

          -  Written informed consent.

          -  Histologically confirmed, resectable American Joint Committee on Cancer (AJCC, 8th
             edition) stage IIIB, IIIC (Tx, T0, T1-4, N1b, N2b, N3b, M0) cutaneous melanoma or
             unknown primary melanoma with sufficient cutaneous and/or nodal disease to enable
             multiple excisional or core biopsies (at baseline, week 1 and week 2). 'Resectable'
             tumours are defined as having no significant vascular, central nervous system or bony
             involvement. Only cases where a complete surgical resection with tumour-free margins
             can safely be achieved are defined as resectable. Patients who may not have sufficient
             disease to enable multiple biopsies at weeks 1 and 2 will not be excluded, however the
             intention of the study is that at least one biopsy at these time points is required.

          -  Measurable disease according to RECIST version 1.1 criteria (≥ 10mm longest diameter
             for non-nodal lesions and / or ≥ 15mm in shortest diameter for lymph nodes) within 4
             weeks of randomisation. 'Measurable' disease may be ascertained by CT or for cutaneous
             and superficial lesions, by caliper measurement with digital photography. CT preferred
             for all lesions where possible. PET imaging will be performed, but not used for the
             primary purpose of measuring response.

          -  BRAF V600 mutation positive on immunohistochemistry or a local molecular test (e.g.
             Oncofocus): a. A positive V600E immunohistochemistry stain at study entry should be
             formally quantified with a local molecular test following study entry (e.g.
             Oncofocus); b. Molecular BRAF mutation status should preferentially be confirmed using
             tissue taken from the presenting stage III / IV disease. Alternatively, archival
             primary tissue is also acceptable to confirm BRAF mutation status.

          -  Able to swallow and retain oral medication

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0-1

          -  Demonstrated adequate organ function as defined:

               1. Absolute neutrophil count (ANC) ≥1.5 109/L

               2. Platelets ≥100 109/L

               3. Haemoglobin ≥90g/L

               4. Serum creatinine OR measured or calculated creatinine clearance (CrCl)
                  (Glomerular filtration rate [GFR] can also be used in place of creatinine or
                  CrCl) ≤1.5 X upper limit of normal (ULN) OR ≥60 mL/min for patient with
                  creatinine levels > 1.5 X institutional ULN.

               5. Serum total bilirubin ≤ 1.5 X ULN OR Direct bilirubin ≤ ULN for patients with
                  total bilirubin levels > 1.5 ULN.

               6. Aspartate transaminase (AST) and Alanine transaminase (ALT) ≤ 2.5 X ULN OR ≤ 5 X
                  ULN for patients with liver metastases.

               7. Albumin >25 g/L

               8. International Normalized Ratio (INR) or Prothrombin Time (PT)

               9. Activated Partial Thromboplastin Time (aPTT) ≤1.5 X ULN unless patient is
                  receiving anticoagulant therapy as long as PT or PTT is within therapeutic range
                  of intended use of anticoagulants. ≤1.5 X ULN unless patient is receiving
                  anticoagulant therapy as long as PT or PTT is within therapeutic range of
                  intended use of anticoagulants

          -  Anticipated life expectancy of > 12 months.

          -  Women of childbearing potential: a negative serum pregnancy test within 72 hours of
             first dose of study treatment and effective contraception from 14 days prior to study
             treatment until 4 months after the last dose.

          -  Men with a female partner of childbearing potential to use effective contraception
             from 14 days prior to study treatment until 4 months after the last dose.

        Exclusion Criteria:

          -  In transit disease

          -  Uveal or mucosal melanoma.

          -  Prior anti-cancer treatment for melanoma, except for the following:

               1. surgery for a primary melanoma or previous stage III melanoma,

               2. adjuvant radiotherapy to the primary melanoma resected site or to lymph nodes for
                  previous Stage III disease,

               3. previous adjuvant interferon or ipilimumab for resected stage II or III melanoma,
                  Previous adjuvant treatment with PD-1 inhibitors or BRAF/MEK inhibitors is not
                  permitted.

          -  Received any investigational drug within 28 days or 5 half-lives of the planned first
             dose of this study treatment.

          -  Known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs
             chemically related to the study treatments, their excipients and / or dimethyl
             sulfoxide (DMSO).

          -  Active infection requiring systemic therapy.

          -  Current use of any prohibited medication as described in protocol.

          -  Active autoimmune disease or a documented history of autoimmune disease or a syndrome
             requiring systemic steroids or immunosuppressive agents. Patients with the following
             are permitted to enrol:

               1. vitiligo,

               2. type I diabetes mellitus,

               3. residual hypothyroidism due to an autoimmune condition only requiring, and stable
                  on hormone replacement,

               4. psoriasis not requiring systemic treatment,

               5. resolved childhood asthma or atopy,

               6. or conditions not expected to recur in the absence of an external trigger.

          -  A requirement for chronic systemic steroid therapy (> 10mg/kg per day of prednisone or
             equivalent) within two weeks before the planned first dose of study treatment or any
             on any other form of immunosuppressive treatment. Patients who require inhaled or
             intranasal corticosteroids (with minimal systemic absorption) may be continued if the
             patient is on a stable dose. Non-absorbed intra-articular steroid injections will also
             be permitted.

          -  A known history of another malignancy or concurrent malignancy unless the patient is
             disease-free for a minimum of 1 year, is completely treated and at low-risk of
             recurrence. The time requirement does not apply for patients with successful
             definitive resection or curative treatment of:

               1. Non-melanoma skin cancer (e.g. basal cell or squamous cell carcinoma of the
                  skin),

               2. superficial bladder cancer,

               3. in situ carcinoma of the cervix,

               4. in situ breast cancer,

               5. atypical melanocytic hyperplasia or melanoma in situ

               6. other in situ carcinomas,

               7. multiple primary melanomas, or other treated low risk tumours.

          -  Known HIV, hepatitis B or C virus positive status or history of active tuberculosis
             (testing prior to randomisation is not required).

          -  Administration of a live vaccine with 30 days of planned first dose of study
             treatment. Seasonal influenza vaccines for injection are generally inactivated flu
             vaccines and are allowed, however intranasal influenza vaccines (e.g., Fluad®) are
             live attenuated vaccines, and are not allowed. Any vaccine is cautionary within 30
             days.

          -  Patients with a history or evidence of cardiovascular risk including any of the
             following:

               1. QT interval corrected for heart rate using the Bazett formula ≥480 msec, a
                  diagnosis of long QT syndrome (Roman-Ward or Jervell Lange-Nielsen syndromes)

               2. Taking medications known to prolong the QT interval.

               3. Uncorrectable electrolyte abnormal abnormality (e.g. hypo- or hyperkalaemia,
                  hypomagnesaemia, hypocalcaemia)

               4. Uncontrolled arrhythmias, with the exception of atrial fibrillation which is
                  controlled for > 30 days prior to randomisation.

               5. Patients with implanted cardioverter/defibrillators.

               6. Acute coronary syndromes (including myocardial infarction or unstable angina),
                  coronary angioplasty or stenting within 6 months prior to randomisation.

               7. A history or current evidence of New York Heart Association (NYHA) ≥Grade 2
                  congestive heart failure

               8. A current left ventricular ejection fraction (LVEF) below than the lower limit of
                  normal (LLN).

               9. Any abnormal cardiac valve morphology documented by echocardiogram which in the
                  opinion of the investigator could interfere with the patient's safety.

              10. Treatment-refractory hypertension defined as a systolic blood pressure of >140 mm
                  Hg and/or a diastolic pressure of >90 mm Hg, which cannot be controlled by
                  anti-hypertensive treatment.

          -  Evidence or a risk of retinal vein occlusion (RVO) or central serous retinopathy
             (CSR), including:

               1. Presence of predisposing factors to RVO or CSR (e.g., uncontrolled glaucoma or
                  ocular hypertension, uncontrolled hypertension, uncontrolled diabetes mellitus,
                  or a history of hyperviscosity or hypercoagulability syndromes).

               2. Visible retinal pathology as assessed by ophthalmic examination that is
                  considered a risk factor for RVO or CSR, such as evidence of new optic disc
                  cupping.

               3. Intraocular pressure > 21 mm Hg as measured by tonography.

               4. Evidence of new visual field defects on automated perimetry.

          -  History or evidence of interstitial lung disease or active non-infectious pneumonitis.

          -  Serious or unstable pre-existing medical conditions or other conditions that could
             interfere with the patient's safety, consent, or compliance.

          -  Has known psychiatric or substance abuse disorders that would interfere with
             cooperation with the requirements of the trial.

          -  Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent or an
             agent directed to another co-inhibitory T-cell receptor (i.e. OX-40, CTLA-4).