84 XJS door key cylinder removal

My door handle broke and I need to replace it. I’m trying to take out the key cylinder to put in the other one but I can’t figure out how it comes apart. Does anyone know? I see a little slot in the side (in picture) that may be whats holding it but I can’t see how to slide the back over the slot without breaking it.

I believe there is a roll pin in that slot. It’s gotta come out.

Thanks but I couldnt figure out how to get it out however I discovered that it was easier to swap the lever inside the handle (that had a broken tab connecting the rod) than it was to replace the lock. The door handle I took off the 88 donor car had a clip on the back side of the lock so was a different design anyway.