I'd never realised there were so many different ways of adding sugar to the wort. I'd sort of assumed it was always added in the copper.
"BREWING WITH SUGAR.
Sugar and syrup are used in large quantities, and by many brewers, for all descriptions of ales, porters and stouts, but like raw grain more as adjuncts to than as substitutes for malt. In 1847 sugar was first allowed to be used in brewing, and in 1874 all kinds of sugar and syrup were so allowed; under the head of statistics will be seen how this privilege has been used. The proportion used in any brewing varies greatly, ranging from 5 to 40 per cent. of the entire weight of mashing materials. Brewing with sugar requires far less labour than the ordinary malt brewing does, for the sugar is so easily and so quickly dissolved, either by condensed steam, by hot water, or by hot wort. Some have recommended that when cane sugar is used it should be introduced into the mash-tun with the other materials, in which case it would partly undergo conversion to a directly fermentable sugar, but if there were no other objection there would be the loss in draining to be considered. Often the sugar meets the malt wort in the underback; either it is placed in this vessel in the dry state or it is first dissolved ; in either case the mixed wort is pumped into the copper as a whole. Frequently, however, the sugar, dry or in solution, is let direct into the copper; sometimes a platform or cage holding it is suspended in the boiling wort until the sugar is dissolved. Other brewers add the sugar at a later stage, namely, in the hop-back, where the boiling wort on its way to the cooler dissolves the sugar or mixes itself with the sugar solution. It is preferable that the malt and sugar worts should at least meet in the copper, for thorough boiling of the saccharine material has a beneficial effect, and is a safeguard against its impurities. Moreover, by being so boiled together the two kinds of wort get thoroughly mixed together and with the hop extract, so that a perfect and equable solution is obtained; but if the sugar is placed in the hop- back these advantages may not occur, or may only partially occur, and a sticky wort may pass through the coolers and over the refrigerator, rendering the cleaning of these vessels more difficult. If the sugar wort does not meet the other wort until the fermenting vessels are reached, a preliminary boiling of the sugar wort should certainly have taken place, and even then there will be the difficulty of mixing the two kinds of wort in the fermenting vessels to be considered."
"A study of the history and of the art of brewing" by J. A. Nettleton, 1883, page 39
When were specialist brewing sugars first developed? I'm wondering about that one. Earlier that 1884, in any case. That''s the year of the Garton's advert above.