Complex sentence: In the 19th century, Adderbury House was in the possession of Major Larnach and when his Adderbury-trained horse Jeddah won the Derby at 100-1 and also won at Ascot, the Major gifted the building of the village Institute.
Split into simpler sentences: In the 19th century, Adderbury House was in the possession of Major Larnach. When his Adderbury-trained horse Jeddah won the Derby at 100-1 and also won at Ascot, the Major gifted the building of the Village Institute.