In order to assess each potential participant's suitability for the study based upon the relevant inclusion and exclusion criteria, the first visit will involve a medical consultation (history and physical examination), venepuncture (for full blood examination, lipid profile and biochemistry) and a 12-lead surface electrocardiogram. Baseline measurements of central and peripheral arterial and pulse wave velocity will be made at baseline, and 4 hours following the administration of either placebo, 50mg of metoprolol or a 10mg oral dose of ivabradine. The placebo will contain lactose powder.