There has always been argument about what, in the Royal Corps of Signals, was God's Trade. [No there hasn't. Ed.] The RTG and Yeoman of Signals have always claimed the crown - with considerable disagreement from everyone else. This is because they are not God's Trade.
They merely made up this little ditty when their nail files ran out and their nail polish remover had all been used up as a kind of 'poppers' when they used to bash the shrimp on exercise. God's trade is Radio Operator - and always was. End of!