A couple of years ago my wife and I had split up, and her sister (Lucy) invited me to a BBQ at her house. It was my wife's weekend to have the kids and she had taken them to visit friends near London. I had always got on great with her Sister and having been married for 20 odd years she had always been at our house and us at hers. I arrived at the BBQ mid afternoon and rang the door bell. Lucy answered the door in a pair of jeans and a tight white cotton top, with an apron covering it. She gave me a kiss on the cheek and commented that she was so far behind getting ready, would I mind lighting the BBQ. After 20-30 minutes we were all sorted. I was just finishing off in the garden when I heard Lucy shout out Oh F.....! I went to the kitchen to see her drenched, she had put the cold tap on and it had sprayed off a baking tray all over her front. Luckily she had the apron on and this had protected her a little. Without hesitation I helped her out of the apron and she said she would quickly go upstairs and change before the guests arrived. After a few minutes I needed the loo and the only loo is upstairs so I went upstairs and just as I got to the landing the door to Lucy's bedroom was wide open and she was standing there naked. She was facing the other way and initially didn't see me, but I just stood there staring at her beautiful body. She is late 40's 5'8 tall, slim and I'd say goes to the gym and has an amazing pair of tits (34D). Even when she turned round I just stood frozen admiring her. She jumped a little and commented " was I enjoying my free glimpse?" She then walked towards me and gently closed the door. Soon after guests arrived and the BBQ started to get into full swing. Lucy had changed into a light summer dress which was slightly low cut at the front and when she bent down it would reveal her lacy white bra. Every time I looked at her I couldn't stop thinking about seeing her naked earlier. As the drink flowed I started to think naughty things about Lucy and the more the day went on the more I thought about it. By 11pm most people were drunk and starting to leave and Lucy had let go a little herself and she came over and sat on my knee in the garden. It wasn't before long I could feel myself going hard (OMG, how embarrassing!) Lucy whispered in my ear "was I thinking about what I saw earlier, you naughty person" She then got up and went into the house. I felt terrible this was my wife's sister and she had realised that she was giving me such a hard-on. Minutes later Lucy returned with a couple of drinks and sat back down on my knee. She was soon wriggling on me and asked me if I noticed anything different?, She then moved my hand to her waist and said "see no panties now, I've taken them off and if you are good later you can strip me naked and give me a good fucking!" OMG, my cock was pushing so hard and I was starting to fast forward in my mind to when everyone had gone. Lucy then moved my hand up her dress and guided my fingers to her pussy that was already soaking wet. I touched and played with her, mindful that no-one else could see us. Then Lucy got up and went back inside to the other guests. The little tease. Soon after 1am the last guest had gone and as Lucy closed the door she turned around and let her dress fall to the floor, unclipped her bra and said "So what are you waiting for?" I went over to her and she led me to her bedroom where she wasted no time grabbing my erect cock and starting to give me one of the best blow jobs ever. She then told me to lie on the bed and straddled me, gently lowering her pussy onto my rock-hard cock. She then fucked me and swung her gorgeous tits into my face so that I could play and suck her nipples. She was soon coming and shouted out that she so needed to be fucked. We fucked several times that night and ended up falling asleep together. The next morning I woke to feel her soft hands around my cock gently wanking it. I was soon hard again and randy as hell. She told me that my wife (her sister) had told her what a good fuck I was and liked it in a morning so was just making the most of the situation. We showered together and then had some breakfast and I said that I needed to make a move. Lucy then jumped on me undid her bathrobe and told me I wasn't going anywhere till I'd fucked her in the garden as she'd heard that I liked fucking outside. She made me fuck her against the neighbours wall and told me to tell her what a dirty little slut she was. God she was possessed, but I wasn't complaining. Eventually I left and I was absolutely cream crackered, but what a night! Since then my wife and I have got back together, but I have a soft spot (or hard-on) every time I see her sister. As I write this story now I am so turned on and yes if she was here I would fuck her. Just as well she is single really.