My girlfriend's incredible request

When I was visiting my girlfriend, she suddenly asked if I would fuck her boyfriend in front of her. She had wanted to do that for a long time and she wanted to surprise him. I have to admit the thought of fucking her boyfriend and knowing how hot it would make her made me really horny, so I went for it. When he came home I fucked him right away, at first he was amazed but you could see in his trousers how horny it made him. But not only him I was so wet when I rode him and could watch how he did it to his mouse with his tongue. Just another really hot fuck. How would you have reacted to such a surprise?