1998 XJ8 at auto electricians- couldn’t fix the stuck gear lever , no start problem. He gave up after testing the usuals as reported here but it has been sent back with no battery power and thus no access to the trunk/boot. Inserting the key in the access point near the XJ8 badge did nada.
If the battery is NOT connected there is no way of charging the battery at the firewall as suggested in some posts.
On the X300s I have owned, I kept spraying lubricant with graphite into the key hole moving key backward/forward until the key turned. I have always gotten the key to eventually turn!
Failing all else - I’ve had success with the key-wiggling thing - there’s a reasonably well documented means of gaining access by removing the license plate and drilling a small hole in the plinth to get access to the operating rod. I think there’s even a video on YouTube…
Is the system not powered via the firewall or starter or alternator, battery or not?
Another thought just struck me…I think OBD2 specifies access to power so you could cobble together a cable with OBD2 at one end and two croc clips at the other and hook it up to a jump-box.
If you don’t use the key in the bootlid latch, it gets sticky/stuck and you need to work the lock to free it up.
I use my key every few weeks to ensure that I am not a victim.
I saw this way too often when I worked at the dealer.
You’ll get no sympathy from me if the lock becomes inop due to lack of use.
Under the bonnet, near one of the fuse panels is a heavy-duty HOT lead under a rubber cap.
You can power-up the car via that.