So it was my wifes (Ang) 50th birthday in a few months time and I didn't know what she wanted. She had put on a little weight, just a few curves and had just joined slimming world for a bit of motivation. I love a few curves but she needed to feel slimmer to feel sexy. I racked my brains as to what to get her and nothing came to mind. Then I saw an add in the paper for a personal fitness instructor. You could buy sessions in units of 5 and I thought it would make a great present. So I called the number and a young man answered the phone. We chatted for a while and I explained that my wife wanted to lose a few pounds as it helped with her self esteem and made her feel sexier. The instructor Kyle was very understanding and said he got a lot of customers who feel the same way. He asked if i had looked at his website and gave me the address. I pulled it up on the pc as we chatted and looked at the profile and services. Kyle pic showed a man in his mid twenties toned and relatively tall. There was a series of links and I asked him a few questions. At the foot of the page was a link to another website which o clicked and it showed Kyle offered male escort services. As a passing question I asked him about it. He explained the that the fitness work was up and down and that he did a bit of escort work as a side line. It paid okay but the hours could be late. We laughed and joked about the "extras" side of that business and he was very open about it and said he had never slept with any clients that he hadn't fancied. The conversation returned to fitness and as a laugh I asked if he had ever been asked about extras in that role! He laughed and said there were quite a few frustrated wives out there but he had to be professional it was after all his job. I was quite shocked and asked if he had never crossed the line. We were getting on really well and the conversation was light hearted. He admitted that he had had a number of very tempting offers and that was all he was saying. We laughed and joked about being caught by the husband. He said that was often a worry but he had had a number of husbands contact him and tell him that they wanted their wives to experience the full service. I was laughing but was suddenly aware that i was aroused. We carried on chatting and I booked a set of five sessions for my wife every Thursday morning from the day after her birthday. Kyle joked and asked if I wanted the full service or just the standard one. I laughed and said the standard one for now would be fine. Life was normal over the next six weeks until the week of my Wifes birthday. I was suddenly all excited. At first I couldn't understand why. Then the conversation with Kyle kept coming back into my mind. I did some research on the internet and read up all about cuckcolding etc. I certainly wasn't one of those. Then there was an article about stag and vixens. That seemed to appeal much more to me. As a stag I love sex but also loved the idea of my wife being naughty with my permission. She could do anything as long as I had given permission before hand and she came home desperately horny for me. I was so horny after reading all about this it was a new world. On the Tuesday we went out for her birthday meal. She had said blow the diet for that night. The local pub does nice grub and its a walk home so we can have a drink. I'd made a birthday card with her 5 sessions all detailed in it. I passed it to her over pudding. When she opened it she laughed. I made a real attempt to make sure she was not upset and thought I was being critical. She said no she loved the idea and that it really would help her. She asked who he was and where did i find him. I explained everything and that he had a website she could check him out when we got home. We walked home a little typsy. I was feeling very horny as always but when we got in Ang grabbed the i-pad and checked out her new personal instructor whilst i made us a mojito. She read all his pages and went on to see his escort work. She asked me if I knew about that and I explained we had had a long chat and he did it to make a few extra pounds no and then. Ang joked about whether he did "extras". I cooly answered that he does but i haven't paid for those! We went to bed and had an amazing although brief session. My wife was on top of me and came almost straight away. It was extremely passionate. The next day I received a text message from Ang. Thanking me for a wonderful night and an amazing present. I said she was worth it. About thirty minutes later I got a second message. Ang said she had checked out his website again and wondered if this was a good idea. I asked her why and she said he's gorgeous and offers extras and that she might get tempted the message was ended with an ha ha. I didn't really know what to say but after ten minutes messaged her back. All I put was well it is your birthday! I received a message straight back. "lol". A few hours later I got another message. "So it's my birthday! What does that actually mean?". I was immediately excited. and replied, "Its your birthday, means I gave you him as a present!". 30 seconds later another message. "what exactly do you mean by that? xxx". I hesitated as to what to put. but simply replied. "I would never tell you how to unwrap a present!" I did not hear anything for about an hour. Then this came through. "Sorry was dragged into a meeting. So I'm allowed to unwrap your present? Really?" I waited for a few seconds and then sent. "Its your present you can do with it whatever you fancy as long as I get to hear all about it?" There was a pause. "Oh my god are you serious?" I was just about to type a quick get out of jail, i was only joking message when another came through. "Thats so bad. I cant believe you have suggested it. I should be so angry with you but I'm horny! I need to go think about this." I didn't respond, I was shaking horny and had to go relieve myself. Ang got home a little later. She had been to the sports store and bough some gym clothing. Nothing much was really said until we went to bed and then with the lights out Ang asked me to explain her present. I laughed and said it was just a fitness instructor and he was going to help her get trim. She reached over and grabbed my rock hard cock. "Oh my god! This really turns you on doesn't it?". She slowly very very slowly started to wank me off. "So are you telling me that if he's cute, and if I like him, your present is to allow me to do this to him?" I had my eyes closed. "It's your birthday present. You have to do whatever you want with it." I couldn't believe I'd actually said those words. Ang continued to stroke my cock. "Really? Im not saying I want to but that really would be okay?" Her voice was very serious. "Yes" was all I could say. She continued to stroke. "So what your saying is that I can do whatever I want with him as long as I tell you all about it?" "Yes, but when I get home I will want you. I will want to fuck you straight away. I want to smell him on you." I was so close to coming I struggled to get out the words. "Oh my god! You're serious!" Ang picked up her pace. I came everywhere more than ever before. Ang kissed me. "Now that we have dealt with that little fantasy can we go to sleep! You're so bad." I grabbed some tissues and wiped my come from all over my belly and neck. "Don't you want me to return the favour?" "No, I think I will save myself for tomorrow!" Ang left it hanging in the air, she was joking but there was a hint of teasing. I left for work early the next day and gave my wife a kiss before I left. As I got in the car i got a message from my Ang. "I will message you when he arrives x" I couldn't concentrate all morning I was so turned on. At 10.30 I got a message. "He here, hes cute! Just doing some warm ups then he is taking me to the park to put me through my paces." An hour later I received a second message. "Wow what a fantastic workout. He's really good put me though my paces. We are in the kitchen drinking water." I replied. "So it was a good present then? Will you unwrap it?" There was a few seconds pause. "Oh shit! Are you being serious? I though this was just a fantasy?" she had typed. "It's your present. Do you want to unwrap it?" I didn't want to push. "He is cute! I wouldn't know what to say to him! Although he has flirted a bit!" I was so hard it was uncomfortable in my trousers. I sent. "If you want to fuck your personal trainer. Then show him this message from your husband. You are my wifes 50th Birthday present. She wants you to strip her naked and kiss every single part of her. She wants you to make her come. She wants you to fuck her slowly building the pace." "Oh my god!" was all that came back for ten minutes. "I just showed him! he standing stark naked in front of me! I don't know what to do!" was the sexiest text I ever received.