Some campaigners have used this research to claim pornography leads to rape – but Malamuth says that is too simplistic.

He draws an analogy with alcohol.

“For some people alcohol simply has the effect of making them more relaxed, letting them have more fun. For other people it’s true that alcohol can increase the likelihood that somebody will behave in a violent way.

“But if I simply make the overall generalisation alcohol causes violence or leads to violence, you’d probably say that’s glossing over a lot of the nuances.

“Similarly with pornography, for some people, it may be viewed as a positive aspect of their life and does not lead them in any way to engage in any form of anti-social behaviour. For some people who do have several other risk factors, it can add fuel to the fire.”