This is a cliché of innuendo, used to bring out the double entendre, whether initially deliberate or not, in a statement. It is also found as a formula phrase 'as the … said to the …', and sometimes the order of the bishop and the actress are reversed. The joke lies in the contrast between the assumed innocence or rectitude of the bishop and the old reputation of actresses for loose living - in the late 19th and early 20th centuries the term could be a euphemism for prostitute. The expression was well established by the 1940s, and well used in radio comedy in the 1950s, but probably goes back at least to the beginning of the 20th century. In the 1940s the comedienne Beryl Reid popularised the alternative 'as the art mistress said to the gardener', a catchphrase used in her role as Monica in the popular radio comedy Educating Archie.