Balun Or No Balun? - Feeding 1/4 wave verticals

I was asked why I use a balun on my vertical antennas when both the vertical & my coax feedline are unbalanced. I take a look inside the balun to see what it is actually doing inside & explain the reasons why I choose to use one, even though it may not be necessary. The Amateur Radio UK channel is run by UK radio amateur M0GQC (James). As the channel name would suggest, the channel focuses primarily on amateur radio within the UK!!!