Cracks between top of bookcase and ceiling - HELP

[Digital Vibe]

About a year ago we had some built-in bookcases built and at the time the finish was well done. Having given the bookcase and the paint time to properly settle and cure, we eventually loaded it up with books and still - all was fine. Over the winter however we began to notice cracks developing where the bookcase met the ceiling. At the time these were being built I knew the carpenter had used what he called ‘flexible filler’ to fill the small gap between the top of the bookcase and the ceiling but the final finish looked absolutely fine at the time. Now - it’s pretty bad. My hope is that this is something I can repair myself but I need some guidance.

I assume I’ll need to carefully remove the filler that remains but need to know the best way to do this in order to prevent further damage. Having done it, what are the next steps and best methods to repair?

Any help is appreciated - photo is attached. Thanks

 

[Crystalclear]

Hi there.

I would recommend locating the reason why there has been moment and fixing it first.
Not enough screws to hold it in place? Structure built weaker than expected, giving way to settling?

After that you cold always use wooden mouldings along the joints ( B&Q) followed up with Caulk, then painted to match as you see fit.

Try these if the gaps are too big.
http://www.screwfix.com/p/stikatak-cork-expansion-gap-inserts-brown-pack-of-18/72555