Mon Mome stayed on powerfully in the hands of Liam Treadwell to spring a 100-1 shock in the John Smith's Grand National at Aintree.
The Venetia Williams-trained nine-year-old moved into the race soon after turning for home and began to stretch away from his rivals after jumping the final obstacle.
The outsider was well clear approaching the Elbow and passed the famous winning post 12 lengths in front of last year's winner Comply Or Die (14-1).
Paul Nicholls' My Will (8-1) was third while former Hennessy Gold Cup winner State Of Play (14-1) was fourth.
Treadwell said: 'It's an absolutely unbelievable finish, I had the perfect run through the race, he jumped brilliant for me.
'It hasn't sunk in yet, all I can say at this moment in time is it is unbelievable.
'A couple of times loose horses fell upsides me and went under his legs but it didn't really affect the horse.
'He gave me such a great ride. He was an absolute pleasure to ride. He is so genuine.
'I had a quick look round but I wasn't really sure how far in front I was.'
There were still plenty in with chances with two to jump but it was Mon Mome - only 10th in the world's most famous steeplechase 12 months ago - who went to the front after jumping the final fence under 23-year-old Treadwell.
Comply Or Die ran a quite brilliant race to fill the runner-up spot under 11st 6lb, while ante-post favourite My Will was far from disgraced back in third.
State Of Play made a number of mistakes but plugged on well to get fourth.
Tony McCoy's mount Butler's Cabin was sent off 7-1 favourite to give the 13-times champion jockey his first National success at the 14th attempt, and although he got round, he never really got involved in a race which remarkably saw two false starts.