Neo IRENIE (NEOadjuvant Ipilimumab, RElatlimab, NIvolumab Evaluation)

COMMON Inclusion Criteria Applicable to all 3 cohorts Inclusion Criteria: * 1\. Written informed consent * 2\. Male or female patients who are at least 18 years of age on the day of signing informed consent. * 3\. Clinically detectable disease, and/or RECIST version 1.1 defined disease, and/or disease confirmed on PET imaging. * 4\. Fully resectable disease defined as having no significant vascular, central nervous system or bony involvement. Only cases where a complete surgical resection leading to tumour free margins and which is safely achieved is considered "resectable". * 5\. Concurrent primary disease and lymph node metastases acceptable provided completely resectable. * 6\. Up to 3 in-transit metastases are permitted as long as these are fully resectable. * 7\. Tumour that is amenable to a newly obtained core biopsy for performance of the multi-omic predictive biomarker model * 8\. ECOG performance status of 0 to 1. * 9\. Adequate haematological, hepatic, renal and endocrine function * 10\. An anticipated life expectancy of \>12 months. * 11\. Women of child bearing potential (WOCBP) must agree to avoid pregnancy or breast feeding for the duration of study treatment. Inclusion Criteria - Cohort 1 only * a. Histologically confirmed diagnosis of cutaneous melanoma or unknown primary melanoma * b. AJCC 8th Ed Stage IIIB, IIIC, IIID cutaneous melanoma * c. No prior systemic treatment for cutaneous melanoma * d. Completion of the multi-omic predictive biomarker model within 14 days (7-10 business days) of planned randomisation. Inclusion Criteria - Cohort 2 only * a. Histologically confirmed diagnosis of cutaneous melanoma or unknown primary melanoma * b. AJCC 8th Ed Stage IIIB, IIIC, IIID cutaneous melanoma * c. Disease progression on neoadjuvant anti-PD-1 monotherapy, where progressed disease is completely resectable or, disease recurrence on adjuvant anti-PD-1 monotherapy, where recurrent disease is completely resectable * d. No prior treatment with CTLA-4 or LAG-3 inhibitors. Inclusion Criteria - Cohort 3 only * a. Histologically confirmed diagnosis of mucosal melanoma * b. Any stage of disease provided it is fully resectable * c. No prior systemic treatment for mucosal melanoma COMMON Exclusion Criteria Applicable to all 3 cohorts * 1\. Uveal melanoma * 2\. Any contraindication to the administration of relatlimab, ipilimumab or nivolumab * 3\. No prior systemic therapy, including treatment with prior anti-PD1/L1, anti-CTLA-4 or anti-LAG-3 therapy (cohorts 1 and 3), except for cohort 2 which will have received anti-PD1 monotherapy only. * 4\. A diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 14 days of randomisation. The following are permitted: 1. Replacement therapy (e.g. thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc) 2. Inhaled or intranasal corticosteroids (with minimal systemic absorption) may be continued if patient is on a stable dose 3. Non-absorbed intra-articular steroid injections. * 5\. An active autoimmune disease that has required systemic treatment in the past 12 months (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). The following are permitted: 1. Vitiligo 2. Type I diabetes mellitus 3. Residual autoimmune hypothyroidism on stable hormone replacement 4. Resolved childhood asthma or atopy 5. Psoriasis not requiring systemic treatment 6. Autoimmune conditions which are not expected to recur in the absence of an external trigger. * 6\. A known additional malignancy that is progressing or has required active treatment within the past 3 years. The following malignancies, if undergone successful definitive resection or curative treatment, are permitted: 1. Basal cell carcinoma of the skin 2. Squamous cell carcinoma of the skin 3. Carcinoma in situ (e.g. breast carcinoma, cervical cancer in situ) that have undergone potentially curative therapy) 4. Prostatic intraepithelial neoplasia 5. In situ melanoma 6. Atypical melanocytic hyperplasia 7. Multiple primary melanomas 8. Other malignancies for which the patient has been disease free for 1 year. * 7\. A known CNS metastases and/or carcinomatous meningitis * 8\. Has a history of (non-infectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis or current interstitial lung disease. * 9\. Has an active infection requiring systemic therapy. * 10\. Has a known history of Human Immunodeficiency Virus (HIV). Note: no testing for HIV is required unless mandated by local health authority. * 11\. Has a known history of Hepatitis B (defined as Hepatitis B surface antigen \[HBsAg\] reactive) or known active Hepatitis C virus (defined as HCV RNA \[qualitative\] is detected) infection. Note: no testing for Hepatitis B and Hepatitis C is required unless mandated by local health authority. * 12\. Has a known history of active TB (Bacillus Tuberculosis). * 13\. Uncontrolled or significant cardiovascular disease including, but not limited to any of the following: 1. Myocardial infarction (MI) or stroke/transient ischemic attack within the 6 months prior to consent 2. Uncontrolled angina within the 3 months prior to consent 3. Any history of clinically significant arrhythmias (such as poorly controlled atrial fibrillation, ventricular tachycardia, ventricular fibrillation, or torsades de pointes) 4. QTc prolongation \> 480 ms 5. History of other clinically significant cardiovascular disease (i.e. cardiomyopathy, congestive heart failure with New York Heart Association functional classification III-IV, pericarditis, significant pericardial effusion, significant coronary stent occlusion, poorly controlled venous thrombosis, etc) 6. Cardiovascular disease-related requirement for daily supplemental ox