Inclusion Criteria (Registration):

          1. Age ≥16

          2. Patients with a diagnosis of Primary CNS Lymphoma (PCNSL) with refractory or relapsed
             histologically confirmed CD19+ PCNSL following standard therapy requiring salvage in
             whom alternative therapies are deemed inappropriate by their treating physician

          3. Agreement to have a pregnancy test, use adequate contraception (if applicable)

          4. Written informed consent

        Exclusion Criteria (Registration):

          1. CD19 negative disease

          2. Evidence of secondary CNS lymphoma

          3. Prior allogeneic haematopoietic stem cell transplant

          4. Active hepatitis B, C or HIV infection

          5. Oxygen saturation ≤90% on air

          6. Bilirubin >2 x upper limit of normal

          7. Glomerular Filtration Rate (GFR) <50ml/min

          8. Women who are pregnant or breast feeding

          9. Inability to tolerate leucapheresis

         10. Karnofsky score <60% (ECOG 0-2 (appendix 3)

         11. Known allergy to albumin or Dimethyl sulfoxide (DMSO)

         12. Life expectancy <3months

         13. Arrhythmias or significant cardiac disease and left ventricular ejection fraction <40%

         14. Pre-existing neurological disorders (other than CNS involvement of underlying
             haematological malignancy)

         15. Any contraindications to PD-1 antibody Pembrolizumab

         16. History of autoimmune disease (e.g. Crohn's, rheumatoid arthritis, systemic lupus)
             resulting in end organ injury or requiring systemic immunosuppression/systemic disease
             modifying agents within the last 24 months

         17. Evidence of active pneumonitis on chest computed tomography (CT) or positron emission
             tomography (PET)-CT scan at screening or history of drug-induced pneumonitis,
             idiopathic pulmonary fibrosis, organising pneumonia (e.g. bronchiolitis obliterans),
             or idiopathic pneumonitis. Prior radiation pneumonitis in the radiation field
             (fibrosis) is allowed (if >24 weeks since the event)

         18. Prior limited radiation therapy (e.g. radiation to bone metastasis for pain control)
             within 4 weeks of CAR T infusion or chest/mediastinal radiation within 24 weeks of CAR
             T infusion

        Exclusion criteria: for CD19CAR T-cell infusion ( Dose 1/i.v. and Dose 2/intraventricular):

          1. Severe intercurrent infection at the time of scheduled CD19CAR T-cell infusion

          2. Requirement for supplementary oxygen or active pulmonary infiltrates at the time of
             scheduled CD19CAR T-cell infusion

          3. Theme 2 only: absence of grade 3 or 4 Immune Effector Cell Associated Neurotoxicity
             (ICANS) following infusion of Dose 1