I (30M) have been with my company for 5 years. My coworker (32F) started about 2 years ago. She is in an open marriage, but their rule is no hookups with friends / cowokers. She's about 5 '7", pale skin, in shape, small but perky ass, and a surprising set of F-cup breasts. We go out for happy hour and will flirt, but we avoid being overly direct and have never been physical. The other night we went out with some other coworkers, but we ended up the last two out. We decided to go to a pool hall and play a couple rounds. The flirting got much more intense than our usual comments in passing. I'd watch her bend over the table for her shot. She knew and would take her time. She backed into me at one point and I could feel my erection pressed up against her ass. She turned around and stared at me, then jokingly stroked the cue. We finished the game and started walking to our cars. On the way, we couldn't keep our hands off each other. We ended up making out before we even made it to the parking lot. Before I knew it, I had her pressed up against the wall, our hands exploring each other. Her hand found it's way to my crotch and she stroked me over my pants. We were there for a few minutes, but it was late and both needed to get home.
The rest of the walk we talked about how we've both wanted this and how we've both thought about fooling around with each other in the office. She's on a work trip this week, but when she gets back, she's getting bent over her desk at the end of the day.