In May our friend Frank came to stay with us. He and my husband Nick have been mates for over twenty years. They've always been close and Nick has often stayed over at Franks when he has to work in London. I was in bed and I knew both men were watching a boxing fight. Feeling thirsty I got up and went downstairs to find the tv on but Nick and Frank were not there. Moving through into the dining room I saw the small lamp lit in the conservatory, and gently moving the door open, I saw something I thought I'd never see. Let me explain, Nick and Frank have in the past been club doorman. They're both very muscular from body building and to coin a phrase, they're very manly men. Lay face down across the small table in the conservatory completely naked, was my husband. Behind him also naked was Frank, and Frank had his, from what I could see, large cock buried deep up Nicks arsehole. It should have shocked me, it should have made me scream out with anger at being cheated on. It actually made me horny. Watching them fuck had the opposite affect on me, to the one I maybe should have had. As they continued having sex with each other, I became hornier and hornier, to the point I put my hand inside the robe I had on and began playing with myself. They didn't know I was there, so I got to see everything. Frank fucking Nick from behind and then as Frank lay on the floor, I watched my husband mount Franks cock and begin to slide up and down filling his arsehole right down to Franks balls. I was on the verge of cumming, so not wanting to be seen or heard I retraced my steps and headed back to our bedroom. Lay on the bed I put two fingers inside myself and used my other hand to frantically play with my clit. Thinking of them fucking, I brought myself to an amazingly strong oragsm. Frank left the following morning and I didn't say a thing then or since. He'll be staying again at the end of this month, I'd love to be involved in some way, but how do I raise the subject without making Nick feel less of a man, and letting him know I've already watched him being fucked....?