Front passenger cap removal

Hatboy Harvey video deals with barrel lock on driver's side front door.

I'm a bit stuck on removing the black cap next to door handle , part 3.

I got part 2 cosmetic colour trim off. It is stopping me releasing Bowden cable and rest of window regulator carrier

There is a bolt 15. Too large a head to remove from through door hole.i.dont.tji k it is connected? Any ideas appreciated.

I don't want to use brute force yet