The investigators will study Radial artery injury and endothelial function following trans-radial cardiac catheterisation. Radial artery injury will be quantified pre- and post- angiography using Optical Coherence Tomography. The participants will also have radial endothelial function assessed using flow-mediated dilatation at baseline, 24 hours, one week, one month and three months post- angiography. Blood will be taken pre and 24 hours post angiography for characterisation of endothelial progenitor cell numbers and function. The hypothesis is that trans-radial catheterisation will cause a reduction in flow-mediated dilatation which peaks at 24 hours and recovers at three months. The investigators hope to correlate the rate of this recovery with peri-procedural progenitor cell numbers.