iOS 6 Modal Segue as Form Sheet Close Previous Modal

iOS 6 Modal Segue as Form Sheet Close Previous Modal

I'm working on iOS6 with storyboards.
I have a button and on tapping it, there's a Modal Segue (with
Presentation as Form Sheet). The problem I'm facing is the ViewController
where we have the button is also a Modal (again presentation as Form
Sheet). When I dismiss the last Modal the previous one is still being
shown.
I'm attempting to dismiss all using:
[self dismissViewControllerAnimated:YES completion:nil];
which clearly doesn't work. Any advice please.
Thanks.