Got in the cat tonight (Vectra C 05 SRI 2,2) and I got a warning light telling me that a rear bulb had gone. I opened the rear light housing and all the bulbs were fine none blown etc.

HOWEVER, the right hand side housing has a bulb that stays illuminated all the time even without the keys in the ignition???

I have tried all the fuses, and they are OK, I have swapped the bulbs and it still illuminates with different bulbs. I have had to take the bulb out now.

Does anyone have any idea what is wrong with it?