George John Frederick Sackville, 4th Duke of Dorset, born 1793,
died from a fall from his horse
while hunting on Killiney Hill, Co.Dublin, 1815, age 21 yrs.
There is a monument on the site.
The title effectively died with him,
since it went then to a middle-aged unmarried cousin, who eventually died 1843.
The titles of Dorset became extinct.