Inclusion Criteria:  Recent stroke or TIA event (<90 days) that is supported by consistency between symptoms and findings on brain magnetic resonance imaging (MRI) or computed tomography (CT). Patients with TIA will be enrolled only if symptoms at presentation were speech problems, limb weakness, or hemianopsia. Diagnosis shall be made by a Consultant Stroke physician.  Stroke classified as cryptogenic following extensive investigations to rule out a cause as per local protocol, but to include at least:  Trans-thoracic echocardiogram A period of at least 24-hour rhythm monitoring with no evidence of AF. MRI or CT-angiography of the brain Sufficient mobility and dexterity to perform an ECG recording on the AW by touching the dial on the watch when worn with the contralateral hand for 30 seconds. Access to a smartphone with Apple-operating system (OS) within their household for syncing with their watch. Participants must be able and willing to provide written informed consent to participate in the study.  Exclusion Criteria:  Documented history of AF or atrial flutter. Expected to undergo heart surgery in the 1 year following the stroke event. Any episode of myocardial infarction, coronary intervention or coronary artery bypass grafting <1 month prior to the stroke event Any other indication for oral anti-coagulation. Patient has a cardiac implantable electronic device in-situ already or is expected to undergo implantation in the 1 year following the stroke event (excluding implantable loop recorder for the investigation of the CS). Previous left atrial (LA) ablation or LA surgery Life expectancy less than 1 year