Exercise Intervention as an Adjunct to Medical Therapy in Newly Diagnosed Patients With Pulmonary Arterial Hypertension

The goal of this clinical trial is to learn if an exercise programme started shortly after diagnosis improves the fitness and mental wellbeing of patients with pulmonary hypertenion over and above medication alone. It will also learn about whether extra support can help patients keep up with exercise in the long term. The main questions it aims to answer are: * Doe exercise improve how far patients can walk over six minutes * Does exercise improve quality of life scores * Does exercise improve mental health scores * Does extra support after an exercise programme help patients to continue exercising in the long term Researchers will compare the exercise programme to a control group (a group of similar patients who do not receive the exercise programme) to see the effect that exercise has. Participants in the exercise programme group will: * Undergo an exercise programme for 12 weeks, starting around 3 months after their diagnosis * They will undertake the exercise programme at home, remotely supervised by the research team with regular contact * Visit the clinic at the end of the programme for checkups and tests * Keep a diary of their exercise and how they are feeling Participants in the control group will: -Still undergo the exercise programme, but this will happen at a delayed time, starting around 6 months after diagnosis, to allow for a comparison between the two groups. Following completion of the exerise programme: * Half of participants will receive extra support to help them continue to exercise * The other half will not receive any additional support * All patients will be reviewed 1 year following the completion of their exercise programme to monitor their ongoing exercise levels.