Atrial fibrillation (AF) is the most common rhythm disturbance of the heart. It can affect people of any age but usually happens as we get older. It can cause palpitations, breathlessness, lethargy, and fainting attacks. It is also associated with an increased risk of strokes. The best treatment for it at the moment involves burning or freezing (ablation) the heart muscle in a part of the heart called the left atrium. The ablation injures the heart muscle around the so-called pulmonary veins and the procedure is called a 'pulmonary vein isolation'. This procedure work in about 60% of people. The study team have found that there are nerve endings in the heart that also cause AF and have shown that ablating these nerve endings also prevents AF. These Nerve endings are known as ganglionated plexuses (GPs). The study team would now like to perform a trial in people who still have AF after the usual pulmonary vein procedure. The study team hope that ablating the nerve endings that cause AF (GPs), we will stop their AF coming back. The study team will compare this procedure to the normal approach of doing the pulmonary vein isolation again