The investigators will use state-of-the-art imaging to look at heart disease in people with haemophilia. Haemophilia is an inherited disorder in which blood does not clot properly because of lack of a key 'glue' blood component (chemicals known as factor VIII or IX). People with haemophilia are 40% less likely to die of heart disease, but it is not known exactly why this is. Understanding heart disease in people with haemophilia is important because better treatments for haemophilia mean that these patients are now living longer, but doctors still don't know if the risk for heart disease in these patients as they age is the same as that for the general population. If these processes are better understand (perhaps less blood clotting is actually protecting the heart from blockage-causing clots), scientists might be able to reduce the risk of heart attacks for everybody. The UK's first photon-counting detector cardiac CT scanner generates detailed images of the heart and its blood vessels by counting individual X-ray photons. Together with artificial intelligence tools, it is possible to extract a lot of information from these images. As people age, fat is deposited in the vessels which supply blood to the heart which forms plaques. Plaques cause narrowing of the vessels, reducing blood flow to the heart, and can also burst (rupture), leading to a blood clot and heart attack. The new CT scan will show the type and amount of plaques, and quantify the risk of plaque rupture, in people with haemophilia; and the investigators will compare this to people without haemophilia. Understanding the role of factor VIII/IX in heart attacks will improve management of heart disease in people with haemophilia, and may also lead to new prevention and treatment strategies that benefit heart health for everyone.