Very quick Instructable because in my 2015 Jaguar XF, all the fuses in the footwell fuse box were permanently live 12V and I wanted my dashcam to go on and off with the ignition swich.

Having searched every forum to find out what other people have done; people with earlier model XFs were able to piggy-back off the 'auxiliary socket' (cigarette lighter) fuse - but my fuse box did not have this fuse, or any fuse which went on and off with the ignition.

Virtually everybody said to use the permanent-live and switched-live connectors near the rear-view mirror/interior lights (using two wires from the sunroof connector). However, I had a very long cable, terminating in a 12V to 5V converter which I had already threaded through to the fuse panel in the foot well (right hand side foot well in RHD car - ie near the accelerator pedal).

On one forum (only one) I found a potential solution hidden in the replies - many thanks Johnnynostars

https://www.jaguarforums.com/forum/xf-xfr-x250-44/...

It works - the next step shows his method.

Step 1: Connecting the Switched Ignition Voltage

The fuse box layout can be seen in the previous step. Note that one wire (grey and red) has been arrowed. This wire is the switched ignition voltage (heading to the auxiliary socket?). It should be protected by a fuse under the bonnet.

With a suitable clip - see photo, you can attach an additional wire to the grey and black wire.

Actually doing it is a nightmare - the fuse box is in a terrible position and it is almost impossible to access. Putting the seat right back, just enables a contortionist to get somewhere near the fuses. I could not fully push the metal slider down into the clip because access for a pair of pliers is so difficult, so I couldn't properly close the clip when I took the photo.

Everything works well. Many thanks to Johnnynostars on Jaguarforums.com for the idea.