While I do not necessarily endorse everything Roger Stone says, there were stories, repeated even by the Times of London, that Nixon had a mistress from Hong Kong. The Times article from 2015 claimed that MI-6 took pictures of Nixon and this woman. Reportedly, she is still alive and living in California.
I choose not to believe that story unless someone can come up with a good deal of hard evidence to prove it. Say what you want about Nixon, but he was no womanizer and he dearly loved his wife.
They source for those was probably Roger Stone.
Roger Stone would very well know some of this stuff. Probably most of DC knew it at the time.