Firstly let me tell you that I love wearing ladies panties. My wife knows and encourages me to wear them during our sex sessions. But she doesn't know that I also like wearing other items of ladies clothing as well. When my wife is out I like to dress up in all her clothes starting with her stockings & suspender belt followed by silk panties and a black micro skirt, I use a black bra with foam filling and a silk blouse over it. My usual habit is to dress up in our bedroom and whilst in front of the full length mirror fantisize that I'm an office girl ready to get groped by her boss. I slip my hand up my leg beneath the short skirt and into my panties and pull my stiff cock out and slowly wank myself. It was during one of these sessions that my story begins. I was at the stage of being spread eagled on the bed with the mini skirt around my waist and my stiff cock sticking out of the leg of the knickers when my mother-in-law walked in. To explain, my wife's mother lives with us and was doing the week's ironing and had brought the freshly ironed clothes in the bedroom to put away. She was dumb struck at first partly because of the nakedness and partly due to my attire. She demanded an immediate explanation and would not leave the room without one. Her manner was such that I felt like a naughty schoolboy and not a forty five year old adult. She said that without a satisfactory explanation she would not only tell her daughter but all our friends that I was kinky. I asked her to understand that my wife understood part of my needs but that I had to have the added parts of dressing up for fulfillment. My mother-in-law sat down next to me on the bed and placed her hand on my naked thigh and said that everyone has special needs but most surpress them if it causes upset for others.I tried to reason that my wife didn't need to know about this.As I was speaking her hand slid towards my, now soft, cock and began to gently massage it back to life. I asked her 'what would it take for you not to speak of this to anyone' She replied 'I think you know' 'OK' I said 'what do you want me to do?' She stood up and lifted her dress up and pulled down her panties and replied 'You can service this' pointing to her hairy cunt 'For a start, and then I will lay out some ground rules for the future, you may be pleasantly surprised I may be able to help you with your dressing up games, in fact I want you to always be dressed as a girl when you fuck me, which will be quite often.