Interior lights

Am I right in saying that when you open the door on a disco 2 the interior lights come on , as mine only seem to come on when I unlock or lock the vehicle ....... For instance if I was driving down the road and I needed to go into a shop I would take the keys out of the ignition , open the door ( no interior light ) but as soon as I press the lock on the fob the lights come on then go out after a few seconds

What if you open a passangers door ???? Have you had a look at the switch on the A post?????