Originally Posted by
flying_blue_white_red
My last visit to the smoking area was mid November last year before a KQ flight - So situation may have changed in the meantime indeed. My bad!
In the other hand, in the thread you posted there is no mention about LHR T4 smoking lounge closure.
According to this website, this place was apparently still open end of June 2019:
Smoking at Heathrow Airport (LHR)
According to the official LHR website, LHR is entirely non-smoking airside so we now have a conundrum where they (LHR) missed it

or it was closed post July, 2019. Hopefully we can get confirmation one way or another from someone passing thru
https://www.heathrow.com/airport-gui.../smoking-areas
Heathrow is a smoke-free airport, in line with British law on smoking in enclosed public spaces.
Smoking is permitted in designated areas outside the terminal building.
However, please be aware that once you have passed through security control, you will not be able to smoke anywhere in the departure lounge.
If you are catching a connecting flight at Heathrow, please note that smoking is not permitted during the connection process. It's only possible to access the outdoor smoking areas by entering the UK (via passport control), and you would then have to pass through security control to return to the departure lounge.
Electronic cigarettes
Passengers are not permitted to use electronic cigarettes within our premises. Where you are intending to carry cigarettes in your hand luggage, please check with your airline to ensure they are allowed on board the aircraft.