'Beep-Beep' after unlocking ??

Hi there people, hope you can help me here.
I've had an 04 TD4 SE (3dr) for a couple of months now, the past week i've noticed that upon unlocking with the fob and opening the drivers door there is (not always, only now and again but getting more regular) a short double beep and the immobiliser LED under the rev counter flashes to the beep.
The beeping only lasts 5-10 seconds and has no effect on starting the engine or anything as far as i have noticed.

Anybody ever had this and is it something i need to get checked out as it says nothing about this in any of the manuals i have.

Thanks in advance for any help.

dying keyfob battery?

Looks like you're right Sadsack. Attached taken from Rave.

yes its the low battery warning ( have you lost your hanbook )

You don't live near road runner do you?

Problem solved, thanks guys.
Couldn't see it anywhere in the handbook.

(Grunt : That may be why the handbook says ACME where it should say Land Rover !!)