Years ago my then missus said, completely out of the blue, me her and her mates hubby were going to watch the speedway in Manchester. I didn't have the slightest interest in speedway but it was her mate's treat so off we went. Women being the conniving bitches they're renowned for in this instance arranged this so her mate could have a Saturday night exchanging bodily fluids with this bloke, free of the fear of being interrupted. Turned out this sort of thing had been going on for yonks. A while later I saw her with this guy and he was quite a catch I suppose resembling Peter Sarsted the singer. I chatted a while with them. That was the only time I met him.
A few years later he turns up on the arm of my cousin at a family do and was introduced to him. We both had that knowing look in each others eyes and despite that when I saw him on his own, completely denied ever knowing me or the other woman from a few years back.
He married my cousin and they've been together 47 years and in the countless family gatherings since the previous behaviour of his was never discussed.