My colleague becomes a bull

This is a true story.
My colleague, I'll call him Dan, has a bit of a thing for my wife. He's always commenting on how nice she is, and flirts with her when he visits. I've seen him naked in the showers at the local swimming pool and know he has a much bigger cock than me. Recently I've been fantasising about them together. I'm just not sure I can convince my wife to try it.
Anyway, recently Dan met a couple in a local bar. They were on holiday in the area. The woman liked him. She flirted openly with him and sent him some photos of herself.
Shortly after the couple returned home they invited Dan to stay with them. Dan has given me a few details about his visit, not knowing that I'm very interested in being cuckolded and watching my wife take a big cock. He told me he fucked the woman infront of her husband on their wedding anniversary. He said the guy gave drinks and looked after him. Dan said he was too embarrassed to tell me more, but he hinted that the guy had acted as all cuckolds should, and serviced the bull. Mmm I wanted to hear more. Dan said he'd fucked the wife in a tent in the garden. The cuck had wanted to come in but they told him he had to stay outside :-)
We've been messaging each other regularly. I think he enjoys telling me about it. He told me the husband had filmed them fucking. I said I thought the husband was very lucky to be allowed to watch. After a few drinks one night I suggested Dan tied the husband to a chair and fucked the wife right in front of him. I hope he has started to work out that I'm desperate to be cuckolded too.
I am now certain Dan has a thing for my wife. He sometimes drops in and last time he asked where my lovely wife was. Once he popped round while we were working in the garden. I was out back and could hear them talking. I left them to it, enjoying the sound of them laughing. I hope he was making fun of me and she was laughing at his jokes.
My fantasy is to be made to show him my cock in it’s chastity cage. I’d have to strip naked in front of them and he’d laugh at my cock straining in it’s cage.
I am now planning to show him naked pictures of my wife. He has sent me pics of the married woman he is seeing. I’d like to show him my wife’s breasts and encourage him to stroke his cock over them. Of course I’d be wearing my cage.
He is going to visit the couple again next week. I am going to send him a message with a few of my ideas.

Update
Over the past few months I’ve been hinting to my colleague that I’d like to watch my wife get fucked. When she was out at her work Christmas party I wrote to him about her getting drunk and staying out late, and that I was left at home on my own, wondering what she was up to. Then I decided to make it really obvious to him. I wrote telling him about her giving to charity in Africa, and joked that she’d always wanted a black baby. He wrote, “it’s good she doesn’t want a black man”. So I replied “who said she doesn’t?” And then I sent him a series of photos I’ve made where I’ve photoshopped our faces onto them. It’s the cuckold scene with Katie Kox and Shane diesel. Some of them were clearly for fun, obviously photoshopped, but a few I’d managed to do really well, and they looked pretty good. Dan was laughing but I was so turned on. In some of the picture the cuckold husband, me, was holding his wife’s big tits as she got fucked, or kissing her while she stroked the bull’s huge cock.
Dan wrote that he hoped I didn’t have any of him. That got me thinking and so I made a series with katarina hartlova and put my wife’s and Dan’s faces on them. It felt incredible sending him pictures of him “fucking” my wife. I still can’t believe I did it, but it was such a turn on. We joked about my wife looking good and how she’d make a good porn star.
I’ve continued to send him various pictures, including one of her with several big cocks. I wrote she was out partying again. I also sent one with a speech bubble, asking if he wanted to play.
He commented that they looked very realistic.
I get turned on knowing that he has seen us in a cuckold scenario. He knows something humiliating about me.
He asked if he could come round for coffee the other day but I wasn’t home. I’m thinking of inviting him next week. I’ll wear my chastity cage and have the wife’s real pictures ready to show him.

Update
nothing has happened yet, but I’m enjoying working on setting my wife up with my colleague. I think she’s becoming interested in him. He makes her laugh and openly flirts with her in front of me. She flirts back, laughing and slapping him on the arm. I’ve mentioned to her that he likes her. I asked her if they were friends on Facebook. She said no but obviously liked the idea and not long after sent him a request. I wrote to him, saying it was good they were friends. He wrote back, jokingly saying I should watch out, as he has a thing for married women. I wrote “sounds exciting “.
He wrote the other day, asking if I was home. I wrote that I was out, but the wife was home if he wanted to pop round. And he did. I loved the thought of them flirting with each other.
The other day he said we should go for a beer soon. When I said I couldn’t, he said “your wife said she’d go with me if you don’t”. I replied “that’s fine with me”. Mmmm I’m sure we’re getting close. The other night the wife wanted to talk about another man fucking her. We got so excited, and I told her how I’d be locked in my cock cage, kneeling on the floor, watching her riding a big cock. She told me she’d love to try a bigger cock, and she wants him to cum over her big tits, so she can make me lick her clean. She said the guy would get hard again and he’d push me out of the way. He’d fuck her again and cum deep inside her. She came hard as we talked about it. I was so close to mentioning his name, asking her if she liked him, but I decided to wait. I am enjoying the long build up.
My plan is to invite him round one evening and see what happens.

Uodate:
True story: I have now told my colleague that I want him to fuck my wife. We often write about it over messenger and it gets me so hard. He likes her and would love to be able to fuck her.
I started by saying that the couple he joined were lucky, especially the husband, and that I wished I could try it. He jokingly wrote that he was on his way over. I told him it wasn't me that needed convincing, and that I could send her over to him. We joked about it but it was turning me on. I asked what he'd do to her. He wrote "wouldn't you like to know". I think he will be a good bull.
We often write about her now and I love it when he comments about her big breasts and how good she looks.
We have talked about getting a hot tub and how he'd come round and take her in it. I've told him that I'd like to take pictures.
My wife and I are going away to a health spa for our birthdays. He offered to take my place and I told him he could if he sent me pictures.
I love it that he knows my fantasy. I want to send him her nude pictures but haven't dared to do it yet. I think I'll invite him over and have my iPad open with a picture of her on it. I'd like to watch him jerk off to her pictures while we talk about him fucking her. I want him to humiliate me.
As for going through with it... Unfortunately the wife has said no to swinging at the moment. But I'm still hoping to convince her one day...

update
My wife is not ready for a threesome, which is a shame, because the bull and I have now discussed it many times. I've told him that I want to serve drinks for them while he takes her in a hot tub. I've told him he can have her whether I'm there or not. I fantasize about him taking her, and I've made myself fantasize about sucking his big cock. I've told him I have a small cock and she needs something bigger.
The other day he came round while she was at work. I was wearing my chastity cage. I was so close to taking out my phone and showing him her pictures. He has invited me round to his tomorrow and I want him to humiliate me. I want to be made to strip and kneel in front of him. I'm going to wear my cage and watch while he jerks off over her pictures. I hope he cums over me, while he looks at my wife's big breasts.

Update
So my colleague knows everything now. How I want him to fuck my wife in a hot tub while I stand and serve drinks at a bar next to them. I told him I'd bring drinks and my chastity cage. He laughed and said he'd love to help. He humiliates me at work by talking about hot tubs and swinger clubs. It's embarrassing but it turns me on. The wife has said no to it, so for now I have to make do with writing to him about it. I haven't shown him her photos yet. He didn't believe I had some of her nude photos on my phone so I flashed the screen at him. Unfortunately we were at work and got interrupted just as I was going to give him my phone. I still dream about being on my knees infront of him and sucking his big cock while he looks at the pictures of her big tits.