LOL! 
I used to think that perhaps this was a myth that only related to a certain class of gentleman, perpetuated by actors like Hugh Grant (oh I do love Hugh Grant, bless 'im). But it would be interesting to know if this is everyone's experience of the English character. Anyone care to comment? It's hard to judge when you're English yourself!
A friend of mine is a high-class call-girl. She is very beautiful and works out of a luxury apartment here in Sydney. She is originally from London. I met her through mutual gay friends. She is bisexual herself. I've known her for some years and she has confided in me freely, about her clients. Which brings me to my response to your request. My friend has often commented to me that whenever an Englishman phones her, to make an appointment for a session, as soon as she hears the English accent, she
knows it's not going be
standard missionary sex. She tells me her English clients are invariably
"kinky" (her word). She explains this by surmising that because they have to retain such a restrained, respectable, stiff-upper-lip facade in their everyday business and family life, they seek something out of the ordinary, when they stray. This is just one (professional) woman's personal experience. Doesn't necessarily make it true for every Englishman. Some might say that she is only seeing them at their most depraved.
