Andrew wrote on 28/02/2017 :
That was a waste of £70.

If they are loose, and just sitting on the mortar then a bad
storm with plenty of buffetting (violent up and down air
movements) then they could be dislodged.

I'm not convinced. It would need the wind to get under them, to lift
them off - repointed as they were, the wind cannot get under.

They were rebedded some 15 years ago, but not properly pointed at the
time. I had him round to reflaunch the chimney, as there were
indications below of obvious ingress. His reflaunching entirely fixed
that issue, but he pointed out at the same time, that the ridge needed
to be repointed, but he didn't have time to do it there and then. It
was obvious to me that it needed to be done, so I made arrangements for
him to return.