Brewers didn't share their enthusiasm for all-malt beers. They were mostly happy with the new situation, which allowed them to use unmalted grains like flaked barley or flaked rice.
Brewers have had a bomb thrown among them by the advocates of pure beer. A few months ago, in order to allow time for some experiments, the Beer Materials Committee would not sit as soon as was expected. These experiments have now been concluded, and the results are not quite what the trade expected. When under examination last year, among others, Mr Cornelius O'Sullivan, who is far and away the leading man in the profession, and who is Bass's brewer, declined to commit himself to the assertion that no one could tell by the analysis of beer from what material it had been made. At present he knew of no way by which those materials could be identified. Other brewers of standing went a step further, and said it was a matter of impossibility, as the chemical changes which take plare during mashing, boiling, and fermenting processes entirely masked the nature of the cereals or sugar used. With this the Government officials did not disagree. and so could see no way by which brewers could he checked if a law were passed directing them to state on the labels attached to their barrels from what materials the beer contained in them was manufactured. After a good deal of evidence of this class had been given, the pure beerites asked for an adjournment, as they were unable to carry their case any further just then. There were no more witnesses ready, so the committee agreed. This looked very much as if brewers had come out with colours flying, and they were elated accordingly. The resources of the analyst were not, however, exhausted. Under the supervision of representatives of the pure beer party a number of brewings were made from different materials, and the beers, on being fixed and ready for sale, were sampled, and the samples handed to the well-known chemist, Dr Skidrowitz, to see if he could find out, whether they were all malt beers or whether substitutes had been used. The doctor succeeded at length in being able to tell whether anything besides malt was employed. Thus the revenue objection to a change in the law is overcome, and it seemed to be a formidable objection removed. During the Beer Materials Committee's inquiry a large amount of evidence was forthcoming as to the necessity for using "adjuncts," with malt made from British barley, because the latter had not had sufficient sun. Leading brewers said they could not turn out the bright, comparatively light, and lager-like beers now offered to the public from British-grown grain. Dr. Skidrowitz is quite satisfied that this is a mistake, and the results of the experimental brewings which have been nade corroborate him. Furthermore, the greatest authority on the Continent, Professor Aubry, of Munich, who cannot have a bias in favour of British-grown grain, agrees that British barley is as good as the standard article on the Continent, and that, in his opinion, the British brewer has no excuse for using substitutes. The very best Pilsener beer comes from Munich, and it is to be observed that throughout Bavaria substitutes for malt are forbidden. All infractions of this law are punished by imprisonment plus a heavy fine.
Aberdeen Journal - Thursday 24 February 1898, page 6.
There's lots of fascinating information in there.
No surprise that the brewers, wanting to maintain the status quo, asserted it was impossible to tell what a beer had been brewed from. It sounds a dubious argument to me. And that they hadn't tried very hard to see if they could.
When Dr. Skidrowitz proved that you could, they just changed their argument, claiming you couldn't brew Light Bitters from purely English barley. Note how they are called "Lager-like". I've seen such beers quoted ass being a reason why Lager-brewing didn't take of earlier in Britain. Breweries were able to make something good enough to satisfy the public, with risky expenditure on expensive new plant.
Though it is true that these beers generally included adjuncts to keep both the body and colour light. Burton brewers tended to prefer sugar, while those in London mostly went with maize or rice. looking at late 19th-century grists, it may surprise some that an expensive top of the range Pale Ale contained a greater proportion of adjuncts than the cheapest Milds and Porters.
I've had several reports back from home brewers who have made AK that the flaked maize definitely added to the character, resulting in a light, crisp beer. Sort of, er, Lager-like.
Surely the very best Pilsener comes from Pilsen, not Munich. In 1898 they'd only just about started brewing pale Lager. But, of course, Austria had no Reinheitsgebot so the pure beerites argument would collapse.