Passenger door unlocked due to flat battery

We haven't had much chance to use our Neuvo recently. Went into her today and the vehicle battery is flat.  We have had her on charge until 2-3 weeks ago. But as battery is 13 years old We suspect that's the problem. 

So more testing tomorrow BUT the worry is we can't work out how to lock the passenger door.  It doesn't respond to the remote or the key or the button in the vehicle.  

Obviously can't get a battery until Sunday or probably Monday.  Any one had this problem? Or even better any ideas.

I guess it's fair to assume that you can't get hookup to the van to get some charge into the vehicle battery?

If not, it may be possible to temporarily disconnect the vehicle battery and connect the leisure battery to the vehicle positive so that you can lock the passenger door, then disconnect again and use the physical key on the driver's door to finally secure the vehicle. You do of course have to be sure not to do this while the vehicle battery is still connected, as the leisure battery will try to discharge (very quickly) into the vehicle battery!

Otherwise, depending on location, it may be possible to park another vehicle next to it so that it is not possible to get the passenger door open.

Thank Roopert, I think that is going to try tomorrow.  Car is parked in front so some security from that.  Nothing of value inside so fingers crossed.  I just hoped that maybe there was some other way of locking the passenger door we hadn't thought of.

Ploughlin Thank you   ClariseVera is now fully locked up and we can sleep tonight.

Very useful to know, thank you.