CCTV inspections can identify numerous issues such as tar build up and damaged / failing liners
Badly cracked firebricks and a baffle which is warped and burnt through are replaced
Internal bolts like these on the door glass reatining clips often become sezied and can break when removed. I drill out the old bolts, cut new threads and then fit new bolts
With time the door rope seals will flatten and can become damaged.
I remove the old seals, remove the old glue and then fit new rope
Using a good qualiry chimney inspection camera I can provide HD quality video and still images