Previous research has also found 0.7 to be the magic number.

Dr Barnaby Dixson, a New Zealand anthropologist, carried out similar research in 2010 involving showing subjects digitally altered photographs.

Dr Dixson, whose results were published in the Archives of Sexual Behaviour, said: ‘It is likely that perfect 0.7 ratio sends a biological signal to men that woman is most fertile and most likely to produce a healthy offspring, no matter what size that woman is.