How do i fix slipped chimney coping stones?

[MickyMad]

First post on this forum so please go easy.

I was up on my top floor flat roof extension to fit a new cowl to the bathroom extractor fan and noticed that there is a missing and slipped coping stone to the chimney breast.

There are (were) only 5 stones in total 3 smaller ones sitting on top of 2 larger ones, see attached pics.

Can anyone suggest the best way to rectify the issue?

Would rebedding them with cement be sufficient to hold them fast? I cant see a baton anywhere that may have been used fix the stones to previously.

Should i put a waterproof membrane/felt under them for extra protection?

Many thanks in advance

 

[vinn]

There's no context to your photos. If you could provide some extra photos it would help.

Photos from all four chimney stack sides if its possible.
A photo standing back and snapping as much of the chimney breast and stack as possible. This would provide context.
A photo from in the loft looking up to the gaps in the tiles.

There are a number of obvious issues but dealing with them in context is best.

What condition is the flaunching/terminals in?
Who owns the chimney breast and stack?