Inclusion Criteria:

          -  Participant must be over 18 years of age inclusive, at the time of signing the
             informed consent.

          -  Diagnosis of multiple myeloma with a requirement for treatment as documented per
             international myeloma working group (IMWG) criteria.

          -  Must have at least one aspect of measurable disease, defined as one of the following:

          -  Urine M-protein excretion >=200 mg/24 hours (>=0.2 gram [g]/24 hours), or

          -  Serum M-protein concentration >=0.5 grams per deciliter (g/dL) (>=5.0 gram per liter
             [g/L]), or

          -  Serum free light chain (FLC) assay: involved FLC level >=10 milligrams per deciliter
             (mg/dL) (>=100 milligram per liter [mg/L]) and an abnormal serum free light chain
             ratio (<0.26 or >1.65).

          -  Not a candidate for high-dose chemotherapy with autologous stem cell transplant (ASCT)
             due to presence of significant comorbid condition(s), such as cardiac, pulmonary or
             other major organ dysfunction that are likely to have a negative impact on
             tolerability of high dose chemotherapy with stem cell transplantation, as judged by
             the investigator.

          -  Eastern cooperative oncology group (ECOG) status of 0-2

          -  Adequate organ system functions as defined by the laboratory assessments listed as
             following: Absolute neutrophil count (ANC) >=1.5 x 10^9/L; Hemoglobin >=8.0 g/dL;
             Platelets >=75 x 10^9/L; Total bilirubin <=1.5 x upper limit of normal (ULN);
             (Isolated bilirubin >1.5 x ULN is acceptable if bilirubin is fractionated and direct
             bilirubin is <35%); Alanine aminotransferase (ALT) <=2.5 x ULN; eGFR >=30
             mL/minute/1.73 meter^2; Urine Dipstick for protein OR Albumin/creatinine ratio (from
             spot urine)- Negative/trace (if >=1 plus only eligible if confirmed <=500 mg/gram (56
             mg/millimoles [mmol]) by albumin/creatinine ratio (spot urine from first void); Left
             Ventricular Ejection Fraction (LVEF) by echocardiogram (ECHO) of >=35% participants
             with low LVEF (per institutional standards), consider referring to cardiology per
             local standards of care.

          -  Male and/or female

          -  Contraceptive use by women should be consistent with local regulations regarding the
             methods of contraception for those participating in clinical studies. A female
             participant is eligible to participate if she is not pregnant or breastfeeding, and at
             least 1 of the following conditions applies:

          -  Is NOT a woman of childbearing potential (WOCBP) or Due to lenalidomide being a
             thalidomide analogue with risk for embryofetal toxicity and prescribed under a
             pregnancy prevention/controlled distribution program, and bortezomib having the
             potential to cause fetal harm, WOCBP participants will be eligible if they commit to
             either: abstain continuously from heterosexual sexual intercourse as their preferred
             and usual lifestyle (abstinent on a long term and persistent basis) and agree to
             remain abstinent OR to use birth control as follows: Two methods of reliable birth
             control (one method that is highly effective and one additional effective (barrier)
             method), beginning 4 weeks prior to initiating treatment with lenalidomide, during
             therapy, during dose interruptions and continuing for 4 weeks following
             discontinuation of lenalidomide treatment. Thereafter, WOCBP participants must use one
             method of reliable birth control that is highly effective for a further 3 months
             following discontinuation of belantamab mafodotin, or a further 6 months following
             discontinuation of bortezomib, whichever is longer. WOCBP must also agree not to
             donate eggs (ova, oocytes) for the purpose of reproduction during treatment, during
             dose interruptions and for 28-days following the last dose of lenalidomide, 4 months
             following discontinuation of belantamab mafodotin treatment or 7-months following the
             last dose of bortezomib, whichever is longer. Two negative pregnancy tests must be
             obtained prior to initiating therapy. The first test should be performed within 10-14
             days and the second test within 24 hours prior to prescribing the start of
             lenalidomide therapy.

        The participant should not receive lenalidomide until the investigator has verified that
        the results of these pregnancy tests are negative. The investigator should evaluate the
        effectiveness of the contraceptive method in relationship to the first dose of study
        intervention. The Investigator is responsible for review of medical history, menstrual
        history, and recent sexual activity to decrease the risk for inclusion of a woman with an
        early undetected pregnancy.

          -  Contraceptive use by men should be consistent with local regulations regarding the
             methods of contraception for those participating in clinical studies

          -  Male participants are eligible to participate if they agree to the following from the
             time of first dose of study treatment until 28-days after the last dose of
             lenalidomide, 4-months after the last dose of bortezomib, or 6 months after the last
             dose of belantamab mafodotin, whichever is longer, to allow for clearance of any
             altered sperm: Refrain from donating sperm - Plus either: - Be abstinent from
             heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long
             term and persistent basis) and agree to remain abstinent OR Must agree to use
             contraception/barrier as detailed below: Agree to use a male condom, even if they have
             undergone a successful vasectomy, and female partner to use an additional highly
             effective contraceptive method with a failure rate of <1% per year when having sexual
             intercourse with a WOCBP. Male participants should also use a condom when having
             sexual intercourse with pregnant females.

          -  Capable of giving signed informed consent.

        Exclusion Criteria:

          -  Smoldering multiple myeloma (SMM).

          -  Prior systemic therapy for multiple myeloma, or SMM. NOTE: An emergency course of
             steroids (defined as no greater than 40 mg of dexamethasone, or equivalent per day for
             a maximum of 4 days (that is, a total of 160 mg) is permitted. NOTE: Focal palliative
             radiation is permitted prior to enrollment, provided that it occurred at least 2 weeks
             prior to the first dose of study drug, that the participant has recovered from
             radiation-related toxicities, and that the participant did not require corticosteroids
             for radiation-induced adverse events.

          -  Participant is eligible for high dose chemotherapy with ASCT, as determined by a
             frailty score of 0 as assessed by the IMWG frailty index.

          -  Peripheral neuropathy or neuropathic pain Grade 2 or higher, as defined by the
             national cancer institute (NCI)-common terminology criteria for adverse events (CTCAE)
             Version 5.

          -  Major surgery within 4 weeks prior to the first dose of study drug.

          -  Presence of active renal condition (infection, requirement for dialysis or any other
             significant condition that could affect participant's safety). Participants with
             isolated proteinuria resulting from multiple myeloma (MM) are eligible, provided they
             fulfil criteria.

          -  Any serious and/or unstable pre-existing medical, psychiatric disorder or other
             conditions (including lab abnormalities) that could interfere with participant's
             safety, obtaining informed consent or compliance to the study procedures.

          -  Evidence of active mucosal or internal bleeding uncontrolled by local therapy and not
             explained by reversible coagulopathy.

          -  Current active liver or biliary disease (except for Gilbert's syndrome or asymptomatic
             gallstones, or otherwise stable chronic liver disease as per the Investigator's
             assessment).

          -  Participants with previous or concurrent malignancies other than multiple myeloma are
             excluded. Exceptions are surgically treated cervical carcinoma in situ, or any other
             malignancy that has been considered medically stable for at least 2 years. The
             participant must not be receiving active therapy, other than hormonal therapy for this
             disease. Note: Participants with curatively treated non-melanoma skin cancer are
             allowed without a 2-year restriction.

          -  Evidence of cardiovascular risk including any of following: Evidence of current
             clinically significant untreated arrhythmias, including clinically significant
             electrocardiogram (ECG) abnormalities including second degree (Mobitz Type II) or
             third degree atrioventricular (AV) block; History of myocardial infarction, acute
             coronary syndromes (including unstable angina), coronary angioplasty, or stenting or
             bypass grafting within 3 months of Screening.; Class III or IV heart failure as
             defined by the New York Heart Association (NYHA) functional classification system;
             Uncontrolled hypertension.

          -  Active infection requiring treatment.

          -  Known human immunodeficiency virus (HIV) infection.

          -  Presence of hepatitis B surface antigen (HBsAg), or hepatitis B core antibody (HBcAb),
             at Screening or within 3 months prior to first dose of study treatment. Note:
             Participants with positive hepatitis C antibody due to prior resolved disease can be
             enrolled, only if a confirmatory negative Hepatitis C RNA test is obtained.

          -  Positive hepatitis C antibody test result.

          -  Current corneal epithelial disease except for mild punctate keratopathy. Note:
             Participants with mild punctate keratopathy are allowed.

          -  Intolerance or contraindications to anti-viral prophylaxis.

          -  Unable to tolerate antithrombotic prophylaxis.

          -  AL amyloidosis (light chain amyloidosis), active polyneuropathy, organomegaly,
             endocrinopathy, monoclonal plasma proliferative disorder, skin changes (POEMS)
             syndrome or active plasma cell leukemia at the time of screening.

          -  Exhibiting clinical signs of or has a known history of meningeal or central nervous
             system involvement by multiple myeloma.

          -  Known immediate or delayed hypersensitivity reaction or idiosyncratic reaction to
             drugs chemically related to belantamab mafodotin, or any of the components of the
             study treatment.

          -  Use of an investigational drug within 14 days or five half-lives (whichever is longer)
             preceding the first dose of study drug.

          -  Plasmapheresis within 7 days prior to the first dose of study drug.