I am 3 years into my second marriage with a lovely lady called Denise. We have a good sex life with no problems. Denise, 57, is a senior manager for a large firm and frequently attends social events. A few weeks ago she had one of these at a pub and I promised to pick her up at closing time so she could have have a drink. I turned up earlier than planned, couldnt find her inside, so went out into the pub garden. I saw some movement behind a gazebo so went to look. There to my surprise was my wife, dressed in a smart suit, stockings and heels being snogged by this younger guy (I later discovered he was 30).He then started fondling her breast as I stood some yards away with an erection starting. This went on for a few minutes before they sat down on a bench and his hand then started feeling her thighs and pushing up under her skirt. He clearly was working a finger inside her as she started moaning and he suddenly stood up, got out a cock a fair bit bigger than mine, spread her legs and penetrated her. I was frozen to the spot, amazed but aroused! Within minutes he had cum, withdrawn, kissed her and gone back in. She tidied herself up and followed him in. I went in a few minutes later and apart from looking a bit flushed she greeted me as though nothing had happened. When we got in the car I noticed a small globule of cum on the inside of her stockings and decided to talk to her about it when we got home. This I did and what happened next will be described in part 2