Throughout the Western world, there has been a dramatic growth in cohabitation between couples prior to marriage since the 1980s.

This was driven, in all probability, by the sexual revolution of the 1960s and 70s.

The idea behind cohabitation, or trial marriages as they were then called, seemed intuitively good.

These couplings would assist boyfriends and girlfriends in knowing how well they got on together in a marriage-like but informal arrangement as a precursor to marriage.

Successful cohabitation followed by marriage should, according to the theory, result in more successful marriages and a reduction in divorce.