Ive been riding my boy for almost 2 years now and last week i started to have problems...out on a hack with 2 others we started to trot,my boy picked up speed to catch up ignoring my command to slow down,head right up trotting straight past at which felt like 50mph..hence now im schooling him with a martingale,others have ridden him since as well as me and said hes fighting them and point blank refuses to give in,and that he might be hard to stop whilst out therefore dangerous,any advice any1 please??