I looked over to see the Prof kneeling on the floor with his arse raised ready to receive me. 'Go on Michael, he's waiting...' ordered Sophie, a little fiercely in that posh accent. I went over and positioned myself behind him. I grasped my cock and pushed it towards his arse hole, but it skidded on the lube and slid up between his cheeks. The Prof gasped in frustration. 'Go on Michael' Sophie barked 'Go on' I tried again, but a combination of over excitement and almost a fear of something I hadn't done before caused my cock to soften. People without big cocks don't know how difficult it is to manage them. They are not like small ones which fill up and get rock hard in a second, they get hard gradually and the very hardness difficult to get a straight up erection because of the weight of a big cock itself. Anyway mine was drooping, and this wasn't a situation Sophie would tolerate. 'Oh my goodness, get over here now.' She beckoned me over to where there was a long footstool. 'Lay on this' I did as instructed with my back on the stool and my legs open, with my feet spread on the floor to get my balance. 'Right we'll get this fixed.' Sophie positioned herself kneeling between my legs and reached forward grabbing my cock with one hand and my balls with the other. With a few gentle strokes of the shaft made in time with gentle squeezes of my balls my cock rose. I went to get up, ready to resume, but she pushed me back. 'No it's not that easy Michael, I'm going to make sure you really want it this time.' Holding my cock at its base with one hand, she used the palm of the other on my knob head. She rotated her palm all the way round the glands giving me exquisite bursts of pleasure. I felt the sperm churning in my balls as it started its journey through my cock, but I couldn't orgasm - it just came in waves of pleasure right up to the brink and then stopped before another wave began. It was all too much and Sophie found it difficult to continue her movements because I was jerking and twitching so much. I almost fell off the stool. Sophie looked towards the Prof who was watching and slowly playing with his cock. 'Richard get over here and hold him down, and Michael if you can't stay still I may have to tie you.' The Prof squatted over me facing my cock and lowered the weight of his body full on my chest. I couldn't move and Sophie resumed her work. After what seemed a lifetime of this erotic torture she stopped. For a moment she admired my rock hard erection. ' Right Richard kneel down, and Michael go and fuck him.' As I moved towards him, Sophie grabbed my arm. 'Michael you mustn't cum too quickly, he needs a good fucking - put these on.' In her hand she held three rubber cock rings. 'They will keep you hard and delay you cumming. You can take them off when I say.' I quickly slid them over my cock and balls and moved towards the Prof. Even with a rock hard cock and plenty of lube it was more difficult getting into the Prof's arse hole than Sophie's, but once through the tight entrance my cock slid up his tube to the hilt. He grunted as it reached the top. I started slowly and then quickened into a steady rhythm. Sophie was encouraging: 'Good boy Michael, good boy..' I pounded on and on, while the Prof's grunts followed each thrust. Sometimes I felt myself cumming, but when the spunk got to the base of my cock the rings stopped it spurting. Suddenly Sophie was alongside and the Prof shifted onto all fours as I kept my cock well inside his arse. In a moment she was beneath him sucking his cock. He started bucking ferociously but I grabbed his waste and kept fucking. It was obvious when he came because he collapsed forward almost smothering Sophie and ejecting my cock. I noticed some cum dribbling down the side of Sophie's mouth as she spoke. 'Well done Michael, now it's your turn.' She stood up with breasts drooping down to her stomach. ' I'll just get the strap on.'