Complex sentence: Scotty has also taken part in a number of mascot races, the first at Windsor Race Course when he managed 3rd place, and the second at the Annual Mascot Grand National at Huntingdon Race Course when he finished 6th.
Split into simpler sentences: Scotty has also taken part in a number of mascot races. The first at Windsor Race Course when Scotty managed an impressive 3rd place and the second at the Annual Mascot Grand National at Huntingdon Race Course when Scotty finished 6th.