Quote Originally Posted by bowser View Post
It always used to be the case that "Irish Guinness" had to come from Ireland, so almost everything made in Dublin was exported around the world, and lots of what was sold in Dublin actually came from Park Royal in London !!
"Dublin makes five or six principal versions of Guinness, in a total of 19 variations, and exports around 40 percent of its output." (Michael Jackson's Beer Companion (1993), p 181)

60% of Guinness output therefore went to the domestic market (and that book was written in 93, the brewery in London didn't close until 2005). I very very much doubt that ANY Guinness from London has EVER been sold in Dublin, although if you have a source for that, I would be happy to stand corrected.