Source: Nick Hiams (firstname.lastname@example.org), HBD #1790, July 25, 1995
It is suggested that a yeast starter is made from a bottle of Guinness. As you probably know Guinness is bottle conditioned still (in the stuff available in pubs at least). This is supposed to be a very good strain for all top fermenting English beers too.
This recipe is supposed to give between og 1045 to og 1053 depending upon efficiency.
The Guinness available on draught in pubs in England is a "keg" beer which has an og of around 1036 (Dilute the above to 6 galls). It is unusual and different to the bottled version in that it is injected with Nitrogen instead of Carbon Dioxide. This has been tried with "a remarkable degree of success" by the author of the book. Personally I prefer the bottled stuff.
I tried the recipe about five years ago and remember it as being a very good imitation. I served it from a barrel as a cask conditioned ale (is this what the Irish version is like?). All of the beers in the book that I have tried or friends have are very true to the originals and I can thoroughly recommend it.