“The better the sex, the better the chances of conception,” Dr Joanna Ellington, an American expert in reproductive physiology, says in the programme, The Great Sperm Race. “One of the things that men don’t realise is that the more excited they are, the further back in the testicle they are going to draw on reserves [of sperm]. So if you have what I call ‘gourmet sex’, where you really spend time and you make it fun for both partners, that is going to make the man more stimulated and he is going to ejaculate more and healthier sperm.”

The research tallies with previous studies showing men who have viewed pornography just before ejaculation also produce greater amounts of sperm.