Gold Cup day
It as big as big as Robbie v Gary or Cheryl v Kylie.
Today two of the most famous race horses go head-to-head at the Cheltenham Festival.
Millions will be bet on Kauto Star and Denman ahead of their battle in the Gold Cup.
Away from the racecourse and they are actually best mates and have stables next door to each other!
Heart's Kate Justice went to meet them and their trainer Paul Nicholls:
Racing legend John McCririck gave Heart is take on the battle of the two:
Hear John McCririck on the Gold Cup