As PPCI is time critical and delay in treatment can be detrimental to clinical outcome, informed written consent will not be possible prior to the procedure. However, verbal consent using an abbreviated patient information sheet will be obtained prior to enrolment. This will be clearly documented in the patient hospital notes and CRF. As soon as possible after the procedure and whenever possible prior to obtaining T3 blood sample, full written informed consent will be obtained. Blood sampling for T1 and T2 will be done through the arterial sheath and therefore should not cause any significant delay or distress. In the unlikely event where a participant deteriorates and loses capacity during the study, they will be withdrawn from the study but data and blood samples obtained with consent will be retained in the study. In such a case, the treating cardiologist will decide whether to continue with the enoxaparin infusion or not. The consent process will be performed by a qualified medical practitioner according to the principles of Good Clinical Practice (GCP) and the declaration of Helsinki. Following consent, details of patient participation will be sent to their general practitioner.