From memory (been a while since I had a P38 - Soon to return another to the fold..!!) this would indicate a 'Mislock'.
It thinks a door/boot/bonnet is open or there has been movement in the vehicle during the 'Superlocking' phase.
Does the dashboard message display show any mislock information or if any doors are open??
I also seem the remember that an alarm beeping indicates low battery in the remote fob...but this could have been from a Defender....as I am sure the P38 tells you this in the message display.