Wiring for rear internal light in a van

[chrisga]

Not sure if this is the right place, mods please feel free to move if required.

While trying to ply line the interior of a new van we have uncovered wiring for internal lights which is good as we'd like to reinstate. However I'm having a right game. There was a 5pin relay wired up which buzzed every so often. This is where I get lost. The van should have lights that come on when the side or rear doors open. The light can also be turned on by a switch on the dash when the doors are shut. The wires we have are, two which look like power, a brown and the red wire from the bulb. That makes four for a 5 pin relay. Have we lost one? The black wire from the light appears to be screwed to an earth.

I can't for the life of me figure out which terminals the wires should go to on the relay to light the light. Are there any auto electricians that could shed any light please. I can give more info if I've missed anything.

Thanks