Intracranial Cerebral Aneurysm [ICA], the ballooning of a blood vessel caused by weakness in the wall or vein of an artery, is a devastating condition for patients and their families and affects around 5% of the UK population, with rupture occurring in 1 in 100,000 people each year. When an ICA ruptures there is a 30% chance of death, and 20-30% chance of permanent neurological damage. The condition is complex and expensive to treat, and current surgical and endovascular techniques both have well documented shortcomings. Cerus Endovascular Limited is developing - NeXsys™ - a patented implant deployed endovascularly and designed to immediately isolate the aneurysm from the circulation in a single step/single device procedure. The innovations of NeXsys™ are that its bi-lobed design occludes the neck of the aneurysm without the need for an invasive, open craniotomy, as required for surgical clipping, and that it maintains the less invasive catheter based approach of coiling but is far less time consuming and eliminates the uncertainty associated with this lengthy procedure. NeXsys™ is predicted to be highly effective, especially in treating aneurysms at the sites of bifurcations, which account for around 70% of all aneurysms and remain the most anatomically challenging to treat. This project aims to demonstrate the safety and efficacy of NeXsys™ in treating ICAs by completing part of the clinical studies required for regulatory approval and use. A successful project will lead to a First In Man trial. On launch NeXsys™ will deliver substantial benefits to patients and reduce healthcare (NHS) costs for both the first intervention and reduces the need for the treatment of recanalisation.