When did doctors notice the problem with infected blood?

The NHS website says that: “If you had a blood transfusion or blood products before 1996, there's a chance you may have been given infected blood. This could mean you were infected with hepatitis B, hepatitis C or HIV.” It adds: “Today, all blood donated in the UK is screened using very rigorous safety standards and testing to protect both donors and patients.” So, when did health professionals become aware of the dangers of contaminated blood? And are investigators satisfied that measures are in place to stop such a healthcare disaster from unfolding again? I went to speak with Tim Wreghitt, a retired consultant clinical virologist at Addenbrooke's Hospital and was working professionally when all this was happening...