3. Patients with and without background hypertension may be recruited. In the case of patients with background hypertension (ie history of fulfilling the diagnostic WHO criteria for hypertension: SBP > 140 mmHg and/or DBP > 90 mmHg) those with both controlled (<140/90mmHg by 24 hour ambulatory BP) and inadequately controlled BP (on 3 anti-hypertensive drugs including a diuretic) can be recruited.