Well if you read it in the Mail it must be true.
Then again the (UK) legal definition of adultery would need re-writing to include gay marriages (should these become law) since it is currently (something like) "full (penetrative) sexual intercourse with a member of the opposite sex who is not the marriage partner" i.e. gay sex is not adulterous - i think ;'they' probably forgot to update the definiton of adultery when homosexuality was legalized back in the sixties. wierd.