Ok so this is what happened. Phil and Pete went out together every Saturday night. Sunday night was the night I went out with them and another of my buddies, John. All four of us were friends from our schooldays so we always kept in touch and met upon Sunday nights in the pub.
One Saturday night, Phil and Pete turned up at the pub where Jess and her friends were drinking. Jess was always very flirty by nature when she was in the company of men, so, when the guys joined the girls at their table, its quite possible that she got flirty with them as she has done in the past, but always in my presence. This is only supposition on my part, but, it is my belief that this is what happened so when the guys offered to walk her home they had an ulterior motive.
The pub they were in was only a ten minute walk from my house and Phil's apartment is a twenty minute walk in the opposite direction. Somehow they ended up in Phil's apartment. Both of the guys knew which pub Jess went to every Saturday night so I find it difficult to believe that they didn't deliberately go looking for her.
It became a regular Saturday night event, except the two guys didn't meet up with the girls in their pub, they would drink elseware, then meet up with Jess at an arranged meeting place after she said goodnight to her friends. They would then take her back to Phil's flat (apartment) for a couple of hours of sex. All this time I knew she was fucking two guys and I got off on it because she came home full of cum and told me all about it. She just gave me two false names and I was none the wiser.
It was a work colleague of mine that drank in the same pub as Jess that occasionally saw her meeting up with Phil and Pete around the corner from the pub and heading off in a different direction to our home. He felt he ought to tell me which he did, he also knew the two guys so he gave me their names.
I still don't know if Jess's friends were aware of her activities but considering the length of time it went on, their suspicions must have been aroused. This is the reason Jess stopped seeing the guys, much as she didn't want to.