"I'm going to say something really dangerous now," warned panellist Jane Caro on Monday night's Q&A. With the special "Festival of Dangerous Ideas" episode having meandered through the pedestrian topics of toy boys, single parenthood and social media bullies, it was a welcome relief.

Asked whether prostitution could be considered a deliberate career choice, Ms Caro - an author, feminist and education expert - said that marriage, in an historical context, could itself be considered a form of the 'world's oldest profession'.

"I would argue that traditional marriage, which included conjugal rights, particularly when women were not able to go to work or were fired when they first got married, and were basically selling their bodies and their reproductive rights to their husband...was a form of prostitution," she said.

"He bought them, by giving her room and board in return."