"She has to have her own little space and she jumps better like that, so I wasn't too worried.
"She jumped quite well although she landed in the water at that jump, but it was good for her as she can get a bit hairy sometimes.
"I wasn't at all confident as you can see what can happen in the jumping game, so it wasn't until she cleared the last fence that I started to believe she was the winner.
"This is the pinnacle of jumps racing so it is very exciting.
"She can go and have a good holiday now and hopefully we can bring her back again next year."
Rathbone created her own piece of history with the win, becoming the first female to both train and ride the winner of the great race having been aboard the Davina Waddell-trained Just The Man when he scored in 2005.
Rathbone is also a part-owner and New Zealand trainer of the recently named Australian Jumper of the Year in Tallyho Twinkletoe that made history last year winning the Australian Grand National Hurdle/Steeple double in the same season for the first time since 1930.
And the first four home on Saturday, the only horses to complete the race, all had strong links to the Whanganui region.
Magic Wonder was bred, owned, raced and trained by Whanganui people, second-placed Napoleon is trained in Whanganui by Kevin Myers, third-placed Shamal is owned and trained in Hunterville, while fourth-placed Des De Jeu was bred in Whanganui.