As an aside, something I discovered on my XK8: when using the key to open the boot, a bit of downward pressure on the lid allowed it to turn. The friction between the locking parts is increased by the push of the rubber seals. Because the key mechanism is usually a bit gummed up as well, the key won't turn. I tried lubricating the lock, but no joy - then I tried pushing the lid down, and it worked.

I've not done it on an XK, but it could be worth a try before trying the external battery points. Just don't push too hard - it's only alloy! And don't push on the spoiler.

 

One of my biggest problems was that the trunk only opens with the key when the battery is dead. However the keyhole is covered by the license plate!!! So I needed to pop out the plate and unscrew the license plate holder to acces the keyhole. I didn't have a screwdriver on me and wasn't to happy about.

The keyhole is covered by the license plate on an XK2010, correct?
What smart solution do people use instead of screwing of the plate?

 

I don't believe the battery has to be dead before the key release is activated - as far as I know, it's a mechanical linkage. And you can use it when the car is in Valet mode (which keeps the hatch and glove compartment locked even when the rest of the car is unlocked) - that's why you should always remove the key blade before handing over the fob if you engage Valet mode and want your belongings to stay safely locked away.

Yes, the keyhole is behind the plate - on mine, the 'plate' is actually flexible plastic (most UK ones are, but this seems a bit more 'bendy' than a normal one), so I can just flex it out of the way. Mind you, I've not actually tried opening it, I just pulled on the plate to see if I could access the keyhole. Something to do in my next round of routine maintenance, I guess.