If you click here, that will link you to a web-page which offers an answer. It suggests that it is probably not connected with Errol Flynn, but rather a Democrat campaigner in the USA also named Flynn.
According to David Viven's Biog."The moons a balloon" it refers to the allegation of rape that was directed at Errol Flyn during the 1930's.
Flynn then became an American anti hero to a certain kind of US student who, after a sexual conquest, would claim to have gone "in like Flynn".