Some London pubs have already figured out that they can legally sell take away beers in plastic cups. So while you can't sit down inside the pub, everyone stands around in the street outside the pub drinking their "take away" beer.
I've noticed this start to happen in SF. They sell you a drink in a coffee cup with a lid and people stand around on the sidewalk outside. I think it's probably completely illegal, but the opaque cup raises legal barriers to search.
It's an open container. Entrances to half the pubs in London are, British weather permitting, perpetually encircled with punters, fag and pint in hand.
Some London pubs have already figured out that they can legally sell take away beers in plastic cups. So while you can't sit down inside the pub, everyone stands around in the street outside the pub drinking their "take away" beer.