I had a very unusual incident today on the last few miles back into town of a longer ride. I was riding along on one of my old steel roadbikes at a steady 20 or 21 MPH, minding my own business, traffic conditions unusually light when just as I passed a side road on my left, a pony and trap driven a portly middle-aged man joined my road immediately behind me going pretty fast (I don't know the stopping distances of a an equine-pulled carriage but I have a suspicious feeling he had no intentions of stopping at the junction or no chance of actually stopping at the stop line). I ignored it and carried on doing my own thing, riding in a strong secondary position at just in excess of 20MPH. As we were nearing town there were now with housing estates on both sides, pavements, a 60Km/hr speed limit at first and then a 50, and pedestrian refuge island in the centre of the road. I could still hear the hooves behind me. The rider then started shouting at me "telling me to get out of his ****ing way" and that "all cyclists are gay weirdos" and that he would "break every bone in my body if he got me if I didn't get out of his ****ing way." I was actually genuinely scared and didn't look back or respond but kept going, head down, in the drops pedalling for all I was worth in top gear with my speed now nudging 30MPH. I had no idea I had that sort of speed in me but I was hoping to drop him but couldn't. As I say I didn't look back but I know from the echo of the hooves he was pretty close. This carried on for almost two miles with him shouting all sorts of rude and insulting things and horrible threats at me before I turned off to go to my home. On hindsight I probably should have got off the road and on to the pavement and let him go but I don't want to be bullied off the road when I feel I was riding in a safe an appropriate manner and doing nothing wrong. I've ridden the road hundreds if not thousands of times in a similar manner without any kind of incident or any other road user getting annoyed. You can't exactly take down the registration number of a horse and report it so I can't go down that road. Are you supposed to yield to a horse joining from the side? I would have thought they had to obey the same traffic laws as every other vehicle?