A 50 year old male engineer complains of frequent headaches around the right temple area over the last 2 weeks. The pain is excruciating and sharp and often starts suddenly, typically lasting one hour. He often will feel nauseous at the same time but has never vomited. He is known to have Asthma and hayfever and feels his right eye has been more watery than the left recently. Drug history includes Co-codamol for back pain and a Salbutamol inhaler.
What is the most likely diagnosis?