Patients due to receive adjuvant anthracycline chemotherapy (planned epirubicin dose >300mg/m2) for breast cancer at four specialist centres in the North of England will be invited to participate. 170 eligible patients will be randomised in a 1:1 ratio, to either enalapril plus usual care or to usual care. Enalapril will be commenced prior to the first anthracycline dose, titrated to a maximum tolerated dose, and continued during chemotherapy. Chemotherapy will continue per usual care; typically six treatment cycles. Patients will have a blood test performed at the end of each chemotherapy cycle to measure cardiac troponin, and at one month following the last epirubicin dose. Investigators and patients will be blinded to the troponin results. Patients will have an echocardiogram at baseline and following their chemotherapy; they will be assessed in a blinded manner by a central Core Laboratory.