Sir Percy dam Percy's Lass won the Group 3 September Stakes in 1988 (and subsequently died of colic when Sir Percy was a foal. Sir Percy was the last of her offspring) and his damsire Blakeney won the Epsom Derby himself in 1969. Sir Percy was named after Sir Percy Blakeney, the hero of the novel "The Scarlet Pimpernel". In November 2003 Sir Percy was sent as a weanling to the Tattersalls sales. He was bought for 20,000 guineas by Will Edmeades bloodstock, acting on behalf of Anthony Pakenham. Pakenham bought the colt as compensation for losing a National Hunt Horse. Sir
Black Knight (Sir Percy) was a master of swordsmanship, horseback riding and all forms of combat known in Britain at the time of Camelot. He was also a talented poet, singer and musician with the lute. Percy wielded the Ebony Blade, and Merlin's spells rendered the Black Knight invulnerable to physical harm as long as he held the Ebony Blade. However, the spells were ineffective against a weapon made of the same metal as the Ebony Blade. He also wore body armor and a helmet which were similarly rendered impenetrable by Merlin's spells. Sir Percy appeared in the "Spider-Man and His Amazing Friends" episode