The light on the left side cupboard in the boot under the shelf is on, but I cannot find a switch. The switch on the right side panel turns the lights in the door on & off, but not this light.
It has a timer of around 10 mins. I replaced mine with an LED one from flea bay. Works well. The original one never drained the battery though so may have been a waste of time
Have you or a previous owner replace the original bulb with an LED bulb. If so the LED version will remain lit when power it switched off due to the residual current in the circuit intended for a conventional bulb. Should go out eventually but remember every time you open the tailgate to check it will charge the circuit again!