iOS - Display a UIViewController as fullscreen from within a UINavigationController

I need to present a UIViewController as fullscreen (Above all other views). This UIViewController is currently inside a UINavigationController.

Is it possible to have the UINavigationController present it's current top UIViewController modally?

From within the UIViewController I would like to fullscreen, if I use:

[self.navigationController presentViewController:self animated:YES completion:nil]

Nothing seems to happen.. Is there a reason this is not allowed?