Just about as soon as it became legal, some British brewers began to use raw grain. Not something to be particularly proud of, but a fact nonetheless. Barclay Perkins, for example. Some of their beers had 10% raw grain, 20% sugar and just 70% malt. That's a similar grist to a DDR Helles.
My source is, again, "Principles & Practice of Brewing" by Walter J. Sykes & Arthur R. Ling, published in 1907.
Mashing with raw grain
Before 1880, the use of raw grain had been illegal in commercial breweries, though some authors had advocated its use amongst domestic brewers.
One method of using raw grain originated in the USA, where grists could consist of 50% raw maize. Maize grits were gelatinised in a "converter" by heating them with a small amount of ground malt to 200º F and keeping them at that temperature for 30 minutes. They were then allowed to cool. The malt was mashed in the standard way and after standing for 60 to 90 minutes the gelatinised maize was added to it. It stood only a very short time before the wort was drawn off, as the gelatinised maize was converted very quickly. Malt made from coarse-skinned barley was used to help filtration in the tun. The malt was dried at a very low temperature to boost its diastatic power. Some British breweries made limited use of this technique.
In Britain it was more common to use raw grains which had already been gelatinised, such as flaked maize, flaked rice or flaked barley. Torrefied maize and torrefied barley were also employed. None of these necessitated a change in the mashing scheme. Between 10 and 20% of the grist could be made up of such material.
In 1900, Barclay Perkins Bitters - PA and XLK - both contained about 10% rice, the darker beers none. By 1910, they had switched to maize, though still only for their pale beers. In 1910 Fuller's grists had between 3 and 6% "flake". Which type of flake isn't specified, though it is clearly some form of unmalted grain, either rice, maize or barley. Whitbread, on the other hand, used no raw grains.
The reason for using raw grain was economy.
"From practical experience one of the authors (A.R. Ling) is unable to recommend unqualifyingly the use of any form of raw grain, prepared or otherwise, as these invariably contain, besides starch, a greater or smaller amount of substances which tend to impair the flavour and stability of the beer. Among these may be mentioned albuminoid bodies which cause turbidity and instability, pentosans which may give rise to thinness and bad flavour, and oil, which, besides imparting an objectionable flavour, exercises a prejudicial effect on the head-retaining properties of the beer. Raw grain cannot be regarded as a malt substitute in the same sense as sugar, the service of which is generally admitted. In the case of the very best beers, any form of raw grain is best omitted altogether, and the authors are inclined to place a limit at which these materials may be used for any description of beer without prejudicing its quality at 10 per cent. of the total grist calculated on the extract yielded."That's pretty clear: don't use raw grain unless you don't mind your beer being crap.
"Principles & Practice of Brewing" by Walter J. Sykes & Arthur R. Ling, 1907, page 519.