The Beatles and cigarette smoking

The Beatles grew up in the heyday of smoking, and Liverpool was known to be inhabited with plenty of especially heavy smokers, even after English sixties smoking standards...
Unfortunately, smoking may lead to serious health problems, as we all know.

Known heavy smokers among people connected with the Beatles:

Their parent generation:
Aunt Mimi (source: Mendips National Trust guided tour host Colin Smith. And in Mendips, Mimi's silver cigarette casing is exhibited)
Harold Harrison (George's father) (died of smoking related disease)
Cynthia Powell's father (died of lung cancer when Cyn was a teenager)
Jim McCartney (photo of Jim smoking pipe in 20 Forthlin Road, and he died in a relatively young age of a smoking related disease - didn't he?)

The Beatles were all heavy smokers during the sixties
Neil Aspinall was also a heavy smoker.
Both George and Neil died of smoking related diseases.

In Liverpool in the fifites and sixties, they smoked everywhere. Buses, cinemas, bars, etc etc

I find it a bit fascinating - in a scary way - to learn how many of the sixties pop idols that smoked heavily... It looks cool to pose with a lighted cigarette, but the price to pay is of course high in the long run ...

I wonder:
At what age did typical Liverpudlians start smoking in the fifties?

How old were John, Paul and George when they started - does anyone know - is there any documentation about this?