21st Lancers
The 21st Lancers (Empress of India's) were a cavalry regiment of the British Army, raised in 1858 and amalgamated with the 17th Lancers in 1922 to form the 17th/21st Lancers. Perhaps its most famous engagement was the Battle of Omdurman, where Winston Churchill (then an officer of the 4th Hussars), rode with the unit.
Read more about 21st Lancers: History