Letters are going missing across London to highlight the need for more new blood donors.
The letters 'O', 'A' and 'B' are going walkabout because these are the names of blood groups. It's National Blood Week, and NHS Blood and Transplant service is saying there are 40% fewer new volunteer donors than there were a decade ago — that means 120,000 fewer people are giving blood across the country.
Blood donation is vital for all sorts of medical procedures. It's not just for emergencies and operations, donated blood is also used in chemotherapy and to give relief to the terminally ill. If you can give blood (find out here) then it's one of the best things you can do. Book yourself an appointment online, and see how easy the process is in our video below — even if you're terrified of needles.