My name is John, and although divorced and living alone I have a very active sex life, mainly with a lady who lives in my road, Peggy who is 72. Peggy and I have been having sex about once a week for nearly a year and I have written about our first few escapades. This story though is about a little show that Peggy's grandaughter Jenny put on for me on Saturday. Jenny is 18 and I have known her for as long as I have known Peggy. She is slim, about 5' 2'' brunette shoulder length hair with a definite 34C bust (I have checked her bra size). She often visits her grandma and we have met on several occassions. I have, at times, I think imagined her flirting with me, even though I am 46 and probably slightly overweight. This has lead to many fantasises about Jenny though the reality is that I thought she would probably run a mile if she knew what I was thinking. On a couple of occassions she has stayed with Peggy over a Saturday night and on one, I went to visit Peggy but because Jenny was staying she didn't want to have sex even though Jenny was out. We therefore just watched TV, but when Peggy drifted off to sleep on the sofa, I went upstairs, firstly to the toilet and then to have a root around in Peggy's spare bedroom. Jenny's things were in her bag, some spare clothes including a white bra as mentioned and a small pair of silky red La Senza panties. Instant hard on followed by a slow wank using Jenny's panties wrapped around my hand. Anyway I am not stupid I knew that that is about as close as I would ever get to Jenny's body. However on Saturday afternoon I went round Peggy's to do a few chores in the garden for her. She let me in, we had a quick kiss and cuddle and then she mentioned that Jenny was in the back garden sunbathing with a girl she was friendly with from the next street. I told Peggy I didn't mind and would just go and clear some of the weeds and cut back some of her bushes as promised. When I went into the garden Jenny said Hi and her friend just smiled a greeting. I have to say it was picture perfect. Jenny had a purple bikini on and was lying front down on a towel and as she spoke I had a clear view past her head and down her cleavage. Her friend, (Vicky) was wearing a black bikini and was also lying on her front, with a book open in front of her and her ear phones in. Fortunately I could see down her top too. Anyway I got on with my tasks and every now and then had a glance at the two girls. At one point Jenny saw me looking and the next thing both girls were laughing out loud and when I looked back both of them were staring at me and then they broke down into hysterics again. After about half an hour, Peggy came out with some cans of drink, coke for the girls and a cider for me. She complained about it being too hot and went back in. The girls though sat up to drink their drinks and I thus got a better look at both girl's tits. What was wonderful was that I could easily make out Jenny's nipples through her top and I felt my cock harden in my shorts as I took furtive glimpses. Half an hour later Peggy came back out to see how I was getting on and I told her that I'd be done in a little while, she then said that she was going to have a lie down in the bedroom as it was so hot and asked, with a wink, if I'd come back this evening. She'd only been gone about 5 minutes when Vicky stood up, shook her towel, slipped on a pair of shorts and a T Shirt, gave Jenny a hug and left via the back gate. I carried on clipping back Peggy's buddleia and when I looked up Jenny had moved to the shade of a large birch tree. She was lying on her back now, head propped up on another towel and staring straight at me. I smiled and carried on working, I glanced back after about 30 seconds and Jenny had her eyes tightly closed now, but now her right hand was actually inside her bikini bottoms and she was obviously frigging herself off. I looked around and realised that Jenny had moved so that she was out of sight of the one overlooking neighbour and the only person who could actually see what she was doing was me. My mouth went dry and my cock grew as I watched young Jenny's hand move around inside her bikini bottoms. I was about 20 feet away but I could tell by her movements that she was actually fingering herself. As I watched her left hand went to her right breast and she half pulled down the bikini cup and I could just make out a small dark nipple which she started to tease with her fingers. Everything within me wanted to rush over and take her there and then, but something told me that I shouldn't. She continued to masturbate, eyes tightly closed all the time and after a couple of minutes she moved her left hand down and used her fingers to ease aside the gusset of her bikini bottoms. To see Jenny's lovely little pink pussy surrounded by a small thatch of pubic hair was too much. I pulled down the front of my shorts and took my cock out. I knew no-one else could see me either and I wanked myself whilst watching Jenny. The fingers of her right hand were pushed inside her cunt and her hand moved ever faster as she frigged herself off. She started to moan slightly and as she did , she opened her eyes and stared straight at me. For about a second I felt like a right dirty old man, but knew that she had wanted me to watch all along. I actually took 2 steps towards her my hand still beating away at my cock, but with a smile she made a quick shake of her head. She then removed her fingers from her cunt and sat up and pulled her bikini top down and then pulled the gusset of her bikini bottoms well away from her pussy. She looked like a picture from some teen porn mag. Her boobs are quite large but nice and pert and her pubic hair well trimmed. On doing that she just sat there and stared at me and I realised that she wasn't offering me her body to fuck but just to wank over. 30 seconds later my cum shot from my cock in long strings of spunk. She smiled and giggled a little and then re-arranged herself, got up and went in doors. I was left with a rapidly deflating cock and a pool of spunk by my feet, but also a wonderful mental image of Jenny. A little while later I went in doors and Jenny was dressed and watching TV and acting like nothing had happened. When I went back that evening Jenny had gone home and Peggy was desperate for a nice long fuck and I couldn't help but keep thinking about Jenny as my cock slipped in and out of Peggy. I am now hoping that I get to see much more of Jenny and that maybe if the weather holds I'll get another show or even more next time.