smudge,
from the compressed view of memory it seems as if they were removed sometime in the mid seventies. As a lifelong non smoker I welcomed the major shift towards non smoking that took place around that time.
Shortly after the 'K' came into service we began to have a lot of air con/pressurisation problems. The groundcrew found that various components in the system, especially the valves, were coated in a dark brown gunge.
In those days pax were allowed onto the flight deck to smoke. Smoking was obviously the culprit in respect of the problems. They brought some samples of the components around to the squadrons and they were not a pretty sight.
If that did not encourage people to give up nothing would.