The dreaded "dead battery, can't open the trunk" situation came upon me this last week with the '04 XK8. Upon researching, I came across the fact that there is an actual key slot in the "XK8" emblem on the bumper ( just to the left of the "X" ) to manually open the trunk in such circumstances. Given my circumstances, I had no other way to address the battery issue except for opening the trunk.
However, inserting they key and turning clockwise or counter-clockwise seemed to do nothing...it wouldn't budge, and I worried about breaking the key by twisting too hard.
Hmmm...
A couple blasts of lithium grease thru the straw attachment into the keyhole and a little time for it to do it's lubricating magic, and I was able to turn the key CLOCKWISE, and with a click I was rather happily met with an open trunk!

So, just some food for thought...maybe try the lock, and you may find it needs a blast or two of lubrication to work properly if you've never has occasion to use it. 10 seconds and some lithium grease may save you quite a bit of headache one day.

 

Don't ya just love a happy ending!

 

 

Much better in the long run to lubricate these locks with powdered graphite vs. lithium grease....

 

^^^^^^ +1

lithium grease is to grit as flypaper is to flies. It can be washed out of the lock to some degree by a spray of electronic cleaner, followed by the powered graphite

Z