After WW I almost no Old Ales were really aged. There were odd examples, but most were just strong and usually dark. You get dark fruit flavours. But they'd be coming from the sugar, most notably, No. 3 invert.
I see they've nicked quite a few of my recipes on that site. If you're interested in more, direct from the source, I've just published a book with 553 historic recipes from WW II.
Blitzkrieg! Vol. 2
The use of roast barley in Irish Stout has nothing to do with tax laws. Before 1880 it was simply illegal to use unmalted grains.
Of the Irish brewing records I have, Guinness is the only one to use roast barley in anything. Perry coloured their Pale Ale - which is what Irish Red Ales are -...
Bottle-conditioned Guinness (RIP) had a definite lactic tang to it. I pity those that never got to taste this wonderful beer. Total world class. And available in every pub in the UK back in the 1980s. Draught Guinness is a very poor replacement.
Everyone had to use a certain percentage for a period during the war and immediately after. I'd forgotten that this rule applied to Park Royal. That's why I said only in the 1980s. Pretty sure that the statement is correct for the Dublin brewery.
There's no contradiction. Guinness, I assume, had to use flaked barley 1941 to 1948, and dropped it when they could. Only to adopt it again when that crook Raunders was in charge in the 1980s,
Guinness didn't use flaked barley for tax reasons. There weren't any tax advantages in using unmalted grain. They used it because it was cheaper than malt. I think they only started using it in the 1980s.
Flaked barley was once common in UK beer. But only because brewers were forced to use it...