Well, I don't know if this is the truth or just a strong rumor, but everyone who responded said, Wyeast 1728 (Scottish). Several confirmed that Alan doesn't not use a bottling yeast, so that sludge is probably what you are looking for.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk