If I was to post two letters in the UK; one with a first class stamp and one with a second class stamp at exactly the same time. This means they are placed in the same mail box. Both letters are heading for the same destination address.
What would be the difference in time between receiving the two letters, and at what stage of the delivery process would the second class letter get 'left behind'?
What would be the difference in time between receiving the two letters, and at what stage of the delivery process would the second class letter get 'left behind'?