@Ticomaya,
Personally, I've never heard of it being illegal, although I haven't seen anyone ordering or drinking one since about the seventies.
As far as I remember, it was lager and cider in equal quantities in a pint glass, no?
We also used to drink stout and cider, same measures. In fact, that was the first concoction I ever got drunk on, and it was years before I could face drinking either cider or guinness.
The only drink I'm aware of being banned in recent times is absynthe (sp?) as it was supposed to give you brain damage or some such nonsense.