I found a very informative video, to find a parasitic drain on the battery.
Very easy test.

 

Just been through this process on my Jeep. Turned out to be one of the DVD screens in the back of the front seats in standby mode.
Never used them so don't know when it got turned on. But the supplier of the battery replaced it under warranty before I realised I had a drain.

 

Good vid. Thanks for sharing . . . but . . .

. . . pls recognize that there is a well documented Jaguar release which we here at JF have shaped into a specific diagnostic tool for our unique vehicles - to be found as Quiescent Current Drain and listed in many of the model specific stickies FAQ or HOW TO . . . under that name.

Unique vehicles? How come? Well -

• Jaguar lays down specific conditions, "sleep" times and thresholds for measuring QCD- a lot more than key out and close all doors;
• with battery in boot/trunk, you may need longer meter leads and close/lock the boot - pls don't lock yourself inside with a torch;
• the boot/trunk dust rubber will cushion the leads, but each new connection to a pulled fuse will need renewed patience until "sleep" time expires.

All this and more, is in our JaguarForums QCD write-up which is an essential pre-cursor to this good video.

Again, thanks for sharing.
Cheers,

Ken