Start off by using the passing crowds to hyperblend on the horse. If you are not familiar with superblending and hyperblending, please see these articles first:
This video took some time so thanks for watching it. You have no idea how many retries i had to do to do the whole thing without being seen.
However every time i attack the target, my PS3 freezes. Also i was wondering if it is possible to air assassinate him from the mast without being seen? I did it before but i was seen.