The gelding, ridden by Tom Bellamy, had led for much of the race but took a horrendous tumble at Valentine's Brook on the second circuit of the famous course..
Celebre D'Allen, a 125/1 outsider trained by Philip Hobbs and Johnson White, weakened in the late stages and collapsed after the last fence, requiring veterinary attention.
Mullins enjoyed the greatest moment of his career as a jockey when he won the iconic race at Aintree on Saturday while on board Nick Rockett after a thrilling contest.