A 75-year-old man is reviewed in the hypertension clinic. His blood pressure readings over the last month average 155/92 mmHg despite taking amlodipine 10mg OD and ramipril 10mg OD. His eGFR is 70 mL/min/1.73m$^2$ and potassium is 4.5 mmol/L. According to NICE NG136, what is the most appropriate next step to improve blood pressure control?