Join between Lime Plaster and Gypsum Ceiling

[TriMattRdg]

I have recently replace gypsum plasterboard with 3 coat lime plaster which has a thinner total thickness .

This has left approx 1cm non plastered section all the way round, between wall and ceiling..

I'm looking for a simple way to repair this.

I

 

[RandomGrinch]

A flexible filler, something like CT1, or Fibacryl...
...or coving!

 

[StephenStephen]

Why not just fill it with lime plaster?

 

[TriMattRdg]

Think I poorly explained it but there is plasterboard , does it just need to be skimmed then along the edge and painted ?