“We spend a lot of time trying to correct the coagulation balance,” explains Professor Michael Laffan, Professor of Haemostasis and Thrombosis at Imperial College London.

Current treatment for haemophilia involves replacing the missing blood-clotting protein by intravenous injection.

“Intravenous treatment can be difficult to do at home,” says Prof Laffan, “especially for parents treating small children – and the effect does not last. Also, 15-20 per cent of patients treat the protein as foreign and respond by producing antibodies.

“An exciting, very new development in trials now, is a molecule that mimics the effect of the normal protein, eliminating the antibody problem. The treatment is subcutaneous, so it’s much simpler, and it lasts for a week or fortnight instead of a couple of days. We may see this licensed in the next year or two.”

There is also “cautious optimism” for the future of gene therapy, in which the protein-producing gene is introduced into the body, where it directs production of the protein, avoiding the need for injections.