And that was about all the Mail on Sunday told us, claiming it was legally barred from revealing the participants.
Pundits who have been told are divided on the significance of the alleged fling, which some claim could have major political ramifications.
One insider claimed it would be as shocking as former Prime Minister John Major's fling with Tory MP Edwina Currie.
But how will this one stack up against the most sensational political sex scandals of all time?
We may never know..