A 56-year-old man of Aboriginal background with type 2 diabetes and persistent hypertension (average clinic BP 158/96 mmHg on three occasions) attends his GP. His urine albumin:creatinine ratio is 8 mg/mmol and eGFR is 80 mL/min/1.73 m². Lifestyle measures over 6 months (salt restriction, weight loss attempts, increased exercise) have not normalised his BP. According to Australian guidelines, which is the most appropriate first-line antihypertensive to initiate?