"It is illegal to be intoxicated in a licensed premises ie. A pub or a bar."
social_inadequate doesn't provide a source for the rest of the laws, so we can't really check their veracity. I can confirm, however, that the above is an actual, and indeed current law, both in England, and here in Ireland (where most of our laws are derived from British common law).
This is not some leftover Medieval law that the police don't know exists: you can be arrested for being intoxicated in a pub. What's more, the licensee (the publican) has the responsibility, as a condition of his/her license, to prevent you from becoming intoxicated.
In practice, of course, the police don't raid pubs looking to bang up tired and emotional people in order to meet their arrest quotas. However, the law can be brought into force to remove somebody from a premises if the landlord thinks he/she has "had enough".