What disease did King George VI die of?

In his later years he was in bad health. He was thrown from his horse which hurt him. He smoked a lot which gave him breathing problems. He had bronchitish and emphesyma. He got very weak and had to take oxygen for the last year of his life. He was actually killed by his doctor so he wouldn't have to suffer any longer (he would have been dead within a few hours anyways). He was given a lethal dose of Cocaine and Morphine (keep in mind cocaine was not used like it is now, and he wasn't addicted to it) in his sleep.