Doctor in the House S06E03 - A Healthy Ship Is a Happy Ship

There is a loss of manpower on the Begonia because Dick has been doling out sick notes or chitties to the crew. Captain Loftus discovers this and threatens to sack him. Industrial action is called. However, when the ship arrives in Madeira nobody wants a chittie, as it would mean missing shore leave. Dick has been fooled by the crew. He has, however, made money by selling the chitties at two pounds a time.