In my experience, this is one of the toughest EC challenges. It needs very high skilled horses and continued effort to achieve. It can take a long time to slowly build up your competition prestige, and a very short time of inattention to lose prestige.

Rather than write the lengthy recommendations here, I will refer you to CapallConnemaras' EC page, where there are already superb guides to this and other EC topics. Well worth studying.

Good luck!

thanks I'll have a look!!