A 52-year-old man attends his GP for a heart health check. He has type 2 diabetes diagnosed 5 years ago, BMI 30 kg/m², blood pressure 148/92 mmHg on repeated measurements, total cholesterol 6.0 mmol/L, HDL cholesterol 1.0 mmol/L and is a non-smoker. His Australian 5-year absolute cardiovascular risk is calculated at 13%. He currently takes metformin only. According to current Australian cardiovascular risk guidelines, which is the most appropriate next step in managing his blood pressure?