[Warning Light] Anti-Theft Device problem

[Cab]

Returned home from a 30 minute trip yesterday. Turned off car and took key out of ignition. Returned to car to remove items and as soon as the back passenger door was opened, the lights turned themselves on, the wipers started going and a message appeared to say that there was a problem with the anti-theft system. Pressing the keyfob made no difference. Eventually, it stopped of its own accord after about 5 minutes. I have seen one posting on a forum from someone with the same problem but no answer. Anybody know what has caused this? My Berlingo is a Multispace 1.6HD 2010 model. Many thanks.