Multiple Navigation Controller Unwind

Hi,

I was hoping someone might be able to help with the following:

I have a NavigationController leading to a UIView for a Login, after that I have a Tab Bar Controller with 4 tabs all with their own NavigationController before the UIViews.

I have a log out button that calls the following:
var storyboard = UIStoryboard.FromName("Login", null);
var viewController = storyboard.InstantiateViewController("Storyboard_Login");
NavigationController.PushViewController(viewController, true);

This works but it gives me the Tab Bar underneath and breaks the navigation after.

Ive also tried:
NavigationController.PopToViewController(NavigationController.ViewControllers[0],true);

But that only works if the tab views don't have their own Navigation Controller, This is because the current Navigation Controller is the one for the tab and I can't work out how to set it to be the one from the Login storyboard.

I've also tried 'pop'ing the view but that doesn't seem to insatiate the Navigation Controller on the Login Storyboard.

I feel like there is a piece of knowledge about how the Navigation Controllers should work so any help would be very appreciated!!