angle

Hi all, I have this on my landing. I recently moved in so I have had to remove the plasterboard due to holes and all the cracking. The previous owner slid the plasterboard in red behind the plasterboard in blue and looks like just plastered the gap to create a curved joint. I want to create a...

Tried everything from super glue to foam. From grip fill to nails. Found the best stuff is polymer mastic. Sticks to everything Inc wet pva. Thin bead of mastic and on with the metal beads and plaster straight away of following day. Whatever. Simple. Holds really well from the start. Like this...