Skimming a plasterboard ceiling

[Brookeh77]

Can someone let me know what would be best to use as a primer if anything at all on this plasterboard ceiling. I ask as I've skimmed plasterboard before which has just flaked off when dry. It looks like the plasterboard has previously been painted and at one point had lining paper on it

 

[Monkey Boy]

Can someone let me know what would be best to use as a primer if anything at all on this plasterboard ceiling. I ask as I've skimmed plasterboard before which has just flaked off when dry. It looks like the plasterboard has previously been painted and at one point had lining paper on it

Prime it with new plaster boards

 

[Brookeh77]

Prime it with new plaster boards

The ceiling has already been over boarded. Any other suggestions? Thanks