The design of the fuel cap on my Tiger Sport means that the key must be left in the cap while it is open. For me and all others I have noticed, that key is on a ring with multiple keys attached. It is a nuisance to have all this rattling around on top of the tank while filling.
I know there is a mod that modifies part of the latch mechanism so the cap stays unlocked and the key can be removed, then fuel cap can then just be closed in the normal locked position after fueling.
I believe this fuel cap is used on all Tiger models, as well as the Speed and Street Triple.
I use a lanyard for my keys. So can take the ignition (fuel cap) key off and the rest are around my neck, no keys flapping about. And when I’m touring I know where the keys are at all times.