Boismoss made his debut in the Wilton Stakes at Catterick in July 1966. His first victory came at Doncaster in the Ayton Stakes in 1967 and he also won twice at Ripon in the summer of his three year old season.
Boismoss became my second runner in a classic when he ran in the 1967 St Leger, but his finest hour was on 7th October 1967 when he won the Cesarewitch ridden by Ernie Johnson. Sent off at 13-1, he saw out the marathon 2m 2f trip to win the race at the age of three.
Boismoss would not win again on the flat and at the end of 1968 he left the yard to go hurdling with Arthur Stephenson.