LE said he is NOT innocent, based on the evidence they discovered. So for those of us who have tried to believe that maybe it was just online flirts but nothing really going on, LE's statement tells us we're in denial and it's far more than that - - they labeled it a "love affair" and uncovered online conversations where they were making plans to meet.
As for when that meeting was to have taken place, and whether it did or not, and whether it was more than one meeting, and whether or not things were already over for some time prior to MB's death, we can only guess. Maybe BB knew about it because MB had ended it and was trying to make amends with BB, and maybe BB mentioned it to LE because a spurned lover (either CW or CWs wife) would make sense as a person pissed off at MB. But in any event, this was certainly not something BB invented.
https://drive.google.com/file/d/0BzeXU7Ui8KyTODIzcUY3SG5nN3M/view