I assume you are familiar with the great American tradition of the "bachelor party."
You know, a fabulous day when men get together to celebrate their soon-to-be-married friend by motorboating the breasts of bored strippers and vomiting in Denny's?
It's an American staple (like Hannah Montana or the PATRIOT Act) because as far as I can tell from watching movies, no man is psychologically prepared to spend the rest of his life with the same woman until he cheats on that woman several days before the wedding.
Apparently, they also have this tradition in England. In America, we encourage men toward adultery and fist-fighting bouncers, but the English celebrate in a markedly different fashion.