Hello; I locked my only set of keys in the trunk today with the alarm set. After quite a bit of searching I couldn't find anything specific to my year and model, but I did find a thread for a 1998 XJ8. Unfortunately that method didn't work; however it did give me enough information to get my trunk open. In that thread they said to use the top right hole of the license plate, and look for a tab to push in. There is nothing there on my 2002.

There appears to be only 3 ways to get the trunk open on these cars if you lock the keys in the trunk with the alarm set. There is a 4th, but I don't recommend it. I read one member say that you can file down the valet key to work.

The trunk button in the cab won't work if the alarm is set, the battery is in the trunk, as is the security locking module, so you can't do it electrically. Here are the 3 ways I know of to get the trunk open.

1)have a spare key or a spare remote that is programmed to the car.
2) have the dealer make a key from the VIN. Approximately $200 where I live. $150 for the key, and $50 to have it cut.
3) remove the rear license plate. There are 6 holes, 2 elongated holes at the top, 2 at the bottom, and 2 round holes in between. Take a long narrow screwdriver and put it in the bottom right elongated hole pointing to the left (towards the lock mechanism). Feel around and poke the screwdriver back and forth. It should pop open. If it doesn't open move the screwdriver from the 9 to the 7 o'clock position while pushing in.
The first time I just had to poke at it, but the second time I had to poke and move the screwdriver from the 9 to the 7 o'clock position. I don't know if it made a difference, but the first time the alarm was set, and the second time it wasn't.

Well I hope this helps you if you unfortunately locked your keys in the trunk with the alarm set.