Obadiah Jones wrote:

"I notice that you have placed an 'it is illegal to smoke on these
premises' sign near the entrance to the Up platform at East Dulwich
station.

Both the entrance ramp and the platform are actually entirely in the
open air, and it is therefore emphatically not 'illegal' to smoke
there.

You are mistaken. Railway Byelaw 3 makes it illegal to smoke on any part
of the railway where there is a notice indicating that smoking is not
allowed. There is no reason to believe these notices can only be placed
in enclosed spaces.

Interestingly, violation of this byelaw is an offence with a penalty of
a fine of up to £1,000, while smoking in violation of the Smoke-free
Regulations can result in only a fine up to £200.
--
Michael Hoffman