I wanted a way to only insert items into the Queue when it was not already added. I want to have a large queue and work my way through it, simply adding as required. Previously I was deleting the queue and recreating on a set time table.
I couldn't find any way of doing this, or any discussion other than 'it's not possible.
I created the method below. I have not used it for huge queues yet, but I post it here in the hope that better options if available might get posted too.