The grey stayed with the pack for the majority of the race before breaking away with Sunnyhillboy and taking victory with the final stride.
Tony McCoy's mount Synchronised, who had been favourite for much of the build-up, was overtaken as the bookies' favourite by Seabass and Shakalakaboomboom as the race's start approached before Katie Walsh's mount Seabass shortened to the 8-1 favourite.
There was drama before the race even started as McCoy fell off Synchronised while the riders made for the start, with the Cheltenham Gold Cup winner galloping away before being caught by a photographer on the course.
The race eventually got underway after a false start 10 minutes behind schedule.
Synchronised then fell at the sixth as more horses struggled to get over the famous Aintree fences, and it was sadly announced later that the Gold Cup winner had to be put down.
Seabass and Shakalakaboomboom took up the lead with Sunnyhillboy and Neptune Collonges chasing down the outside.
Shakalakaboomboom fell away, as did Seabass as Sunnyhillboy, and Neptune Collonges crossed the line neck and neck.
After a brief delay the announcer revealed it was the Paul Nicholls-trained horse, who becomes the first grey to win the National since Nicolaus Silver in 1961, that had snatched the famous steeplechase.