Who can forget the high-fiving chimpanzee, smartly turned out in chinos and blue shirt, cavorting away with Leonardo DiCaprio and his gang of rogue traders in the 2013 biopic The Wolf of Wall Street?

Or Crystal, the drug-dealing capuchin monkey in Hangover II (2011), without which the plot simply would not have worked?

Or the ever-grinning mischief maker Dunston, the orangutan who wreaks havoc in a five star hotel in the 1996 comedy Dunston Checks In?

They are just three examples of a long Hollywood tradition of primate “actors”.

Now, however, scientists have said that using the species in films is 'unethical' and damages their welfare by fooling the public into thinking they are happy in human environments.

A new study by the University of Edinburgh directs particular criticism towards films which feature primates appearing to “smile”, as this is actually a sign of distress.