Doctor in the House S04E01 - The Devil You Know

When Michael leaves St. Swithins, Professor Loftus decides to replace him with Duncan Waring, who has been working as a doctor in Baltimore. When Duncan arrives at the hospital, Dick, Paul and others all pretend to have forgotten who he is for a joke but Loftus is pleased to see him and interested to know what methods he learned in America. One of these is singing during an operation. Loftus and Duncan disagree over treatment during the op but when Duncan is proved right Loftus joins him in playing a joke on the other doctors.